User X is asking rapid-fire questions, sometimes in multiples of same, and then answering/accepting their own. This is annoying on forums and harmful on a Q&A site like this. Make him/her stop.
Answering your own questions is allowed and encouraged, however if you find yourself with a string of Q&A's where you're the only one involved it might be time to step back and examine things. Spend more time on formulating the question, and think about how it might be extended to reach deeper into core issues.
Why? This pattern of talking to yourself tends to be perceived as a reputation gaining ploy. Even though self-answered questions gain no reputation, among other anti-gaming measures, a lot of people will view it negatively and you may not get the results you intended. There is a stigma associated with answering & accepting too many of your own, sometimes the community likes it, sometimes they don't. Follow self answer etiquette and you'll come out on top, overall.
For the record, I personally answer my own questions when I can. If it's taken me more than an hour to figure something out it's worth sharing to help others. Really though, it's delightful to ask a question I think I know the answer to, and have someone else provide a much better one. Consequently I tend to wait a time before adding my own thoughts to allow for such happy occurrences.
My 2bits anyway, others may differ. :)
Yes, stop him, but only if he start duplicating his questions or if the answer is totaly wrong. Having many similar questions with similar answes makes it difficult to find a correct answer if someone search for the same question later on.
Point out in a comment on the question that they gain no points from answering their own. If they are gaming and hadn't realised it got them nothing, they will stop.
There's a secondary abusive scenario, apart from gaming points, are people just trying to get a large list of hits on StackOverflow to enhance their search rankings elsewhere?
I've become more sensitive to this possibility since noticing that my personal Google Alert regularly shows my Stack Overflow postings being copied to other sites.