Not really a major problem but is there a way to be automattically declined from a competition if it becomes full after you already sent your app in so that you're not left with an application thats not doing anything for you.

Not yet. It's been suggested. The host right now has to decline every application. (It was rough for me, I had 99 applicants, and could only choose 5).

All you can do is check to see if an event is full by clicking the event details button, and checking the number that is Total accepted/Total Space Available. If you see they are the same you just remove your application. Sucks, but that's what I've been doing. =P

It will happen.