On StackOverflow it has been the norm to edit out greetings and thanks yous and similar content from questions and answers. The rational being that it just clutters things up. This isn't meant to be a social site, its about exchanging information, not niceties.
My question is simple, is there any reason why we should deviate from this?
I always clean up the Hi/Thanks if I have other things to edit the post for (retags, typos, incoherent babbling, etc) but I generally don't go and edit a post just to remove the salutations.
That said, I don't think it would be a huge problem, but if a user goes and rolls it back I would say it's not a big enough issue to get into an edit war over and just let it slide.
In general removing any greetings before the question is a good idea because it cuts into what people see on the Questions page.
Removing the thanks isn't at the end isn't as important but if you are editing I would remove it for brevity's sake.
Jon Skeet recently wrote about Asking the Perfect Question which talks about not including Hi/Thanks questions. He said specifically
There's no need to include greetings and sign-offs such as "Hi everyone!" and "Thanks - hope to get an answer soon" in the question. These will often be edited out by other users, as they're basically a distraction. Greetings at the start of a question are particularly useless as they can take up valuable space in the snippet displayed in the question list.
Which to me means we need to edit these things out when we can.
