In light of the snake-handling pastor who died this past week, the issue concerning whether the ending of Mark (i.e., 8:9-20) is original and to be applied to us has once again come up. So I want to address both of these issues, from the standpoint of one who rejects its original presence in the text, and from the standpoint of one who sees the text as Scripture (whether it was originally there or not).
First, most scholars don't think this was the original ending of Mark, although there are many who do. The original ending is either understood to be v. 8, or that it had another ending that was lost. I think it's the former rather than the latter.
The reason why I think so is because the theology of Mark emphasizes death. Mark continually records Christ reminding us of His death and that we also need to follow Him in death to Self. In other words, the Gospel communicates the point that following Christ means dying, and this is exemplified in Christ's sacrifice. Hence, the most fitting end is one where the emphasis is on the death of Christ with less emphasis on His resurrection.
Now, having said that, this doesn't mean that Mark doesn't mention the resurrection. It's both in the Gospel and that to which is alluded at the end. The point is on emphasis, not whether Mark thinks the resurrection is important for the overall gospel message and the Christian life.
What I think likely happened is that Mark, being the shortest Gospel, was likely read in liturgy or used as a presentation of the gospel message at some point in the early Church, but was deemed incomplete for that purpose. Hence, a summary made up of the resurrection accounts found in the other gospels, along with some of the things that happened to the apostles was tacked on to give one the gist of what happened after Christ's death. In fact, when you read it, it very much sounds like a summary account of someone who is distant from the apostles and speaks of them in the past tense (a tense gained from context rather than verbs of course).
This brings me to my second point. The summary message is made up of Scripture, so it actually is all inerrant truth. If one were to accidentally include it as original, there really is no mistake that's being made. To demonstrate this, let's briefly take a look at the passage and those texts it uses to summarize.
Now when [He] rose early on the first [day] of the week, He appeared first to Mary Magdalene, out of whom He had cast seven demons.
This could be from any of the Gospels, such as Matthew 28:1-10, but it is most likely from John 20:1-18, since only John mentions Mary the Magdalene alone. This is significant in showing that the summary of Mark here is not just a matter of using Q-like sources similar to the other synoptics, but is also a summary of information found in John (and Acts as we will see). This is another indication that this is a later summary, not necessarily one that is constructed in the time of the apostles.
She went and told those who had been with Him, as they mourned and wept.
And when they heard that He was alive and had been seen by her, they did not believe.
After that, He appeared in another form to two of them as they walked and went into the country. And they went and told [it] to the rest, [but] they did not believe them either.
This is clearly from Luke 24:13-29
Later He appeared to the eleven as they sat at the table; and He rebuked their unbelief and hardness of heart, because they did not believe those who had seen Him after He had risen.
Matthew 28:16-17, Luke 24:36-43, and of course, John 20:24-30 that speaks directly of Thomas' doubting.
And He said to them, "Go into all the world and preach the gospel to every creature.
This, of course, is a paraphrase of Matthew 28:19-21
"He who believes and is baptized will be saved; but he who does not believe will be condemned.
This could be taken from Luke 24:47, or even Matthew 28:19-21, but it is likely primarily taken from John 20:23. In any case, it seems to be a mixture of all of the Gospels together.
"And these signs will follow those who believe: In My name they will cast out demons; they will speak with new tongues; "they will take up serpents; and if they drink anything deadly, it will by no means hurt them; they will lay hands on the sick, and they will recover."
So then, after the Lord had spoken to them, He was received up into heaven, and sat down at the right hand of God.
And they went out and preached everywhere, the Lord working with [them] and confirming the word through the accompanying signs. Amen.
Here we have a summary of things that happen in the Book of Acts. The apostles cast out demons, speak in tongues, Paul is bitten by a serpent when he accidentally picks it up with sticks and is not harmed by it, and they lay their hands on the sick and heal them. The only reference not found in Acts is the drinking of poison, but this was a common form of murdering officials in the ancient world, and it may be that the author wanted to note that the apostles, as God's officials, could not be harmed in that way. He might have gotten that from the idea that serpent poison did not harm Paul. In any case, the rest of the text is definitely a summary of the lives of the apostles. Note, this is what they did. They went out everywhere, the Lord working with them and accompanying them with these signs.
This brings us to the final point. If one accepts this text as Scripture, which I do, even if it is not original to Mark, the correct interpretation of this text is that is a summary of what God does with the apostles. It is not something that is promised to every Christian. I've said before on this blog, God does not throw out miracles left and right throughout Scripture as many think He does. He usually only displays an outpouring of such things in order to establish His Word. Once established, He expects people to listen to it, not seek for signs in order that they might believe (which isn't belief anyway). Hence, these things were for the establishment of the apostolic message and authority we see in the New Testament now, not for all Christians either in their time or ours.
Hence, we can accept the end of Mark as Scripture, since it is a summary of Scriptural truth anyway; but we cannot apply it to ourselves directly, as the text is merely descriptive, not prescriptive, concerning what God does with the apostles. Where it does apply to us is in the prescriptive concerning what the apostles were to do (i,e., go and preach the gospel to all creation). That is the task we pick up from the apostles because it is through our spreading of their message that they complete their task. We are participants in the work they were commanded to do, precisely, because we are the vehicles through which their work will come to completion. But as for God giving us the signs of apostles themselves? That's not for us, as their message has already been established with signs, and now it must simply be proclaimed.
So if you leave Mark in, interpret it in context and for what it is meant to be. If you take it out, no problem, you're not missing anything, as it is essentially all in other places in Scripture anyway. But don't apply it directly, or it may come back to bite you.