I cannot upvote my own stuff (questions or answers). Why is it that I can mark my own question as a favorite? Isnt that like upvoting it? Wouldn't common sense dictate that, as it is my question, it is one of my favorites; i.e., something that I am interested in?
The primary goal of marking something as a favourite is to make it easier to get back to. Yes, there are badges for heavily-favourited questions, but the problem of gaming the system by favouriting your own question is a pretty minor one - but the benefit is real.
Compare this with upvoting, where the primary goal is to say that a post is "good." It makes no sense for you to mark your own post as good - it's purely gaming the system, hence it's not allowed.
People use the favorite list for a very wide variety of reasons. Some use it as a 'mark of honor' - in other words they never use their list, they just like to make sure some questions get a little more attention. Others only add questions to their list that they want to re-read later, or answer later, etc - so they use it as a sort of 'task list'. Some people just mark questions they think they might want to read later but not have to search for.
Keep in mind that users that have been around awhile, or use the site a lot, have hundreds of questions, and it's not easy finding a needle in the haystack.
So a user might mark their own question as a favorite if they want to keep tabs on it over a longer period of time.
I know a few users mark their own question as a favorite to generate the perception of interest - in other words by marking it as a favorite other users are more likely to see that someone found it especially useful, and treat it more favorably than otherwise. This is the only gaming aspect I can think of (aside from the badges, which, frankly, has such a miniscule effect it's not worth considering).
But mainly people who mark their own questions are likely using it as a sort of 'task list' - questions they want to follow over a longer period of time than just a day or two.
Well if it really is your favorite, than mark it as such. I too can get giddy over the thoughts of someone answering my various questions.
In all seriousness marking as favorite doesn't really do anything (other than badge for 25+ where 1 won't be the tipping point). Feel free to mark it as your favorite even if it is your question -- many people already do this. I should also state that this isn't really necessary in that there are alternative methods of finding your own questions with just as much ease.