"Flying Cars" isn't a good answer to your question, agreed, but it is an obvious idea - to everyone.
Chances are that if you are starting a business and you have competition already that they have thought of your idea or something similar and chose not to do it for whatever reason.
My business is www.shelfmade.net - I am now friends with a guy at sharedbook.com. Look how similar the businesses are. I have told him my ideas and he has told me a good deal bout his company. As obvious as I think my idea would be to his company, they are just not into it. They are not going to steal the idea unless I first prove it - then they would know about it anyway.
(Sorry my thoughts are a bit scattered- don't directly address your question, but I'm sure there is a point somewhere)
Glaringly obvious to who? Your start up idea might not seem glaringly obvious to you but don't assume it isn't to your competition!