My partner and I created an iPad game for cats. We wanted to get some extra marketing boost so we contacted friskies (purina). In Nov (2010) I exchanged a few emails, and talked to them on the phone about our game. I sent them a video and they told us they loved the idea and they would get back to us. Then one day, silence. We didn't hear anything for months.
Then a couple weeks ago they released the Friskies "Games for Cats" which are suspiciously similar to our game. The blogosphere exploded. "Friskies releases creative iPad game for cats" "Friskies is oh so clever etc."
We were pissed. But sales improved. A lot.
I tried to track their rankings so I searched for them on the AppStore. Hmm, thats odd. I couldn't find them. It turns out /they didn't make native apps/ they were "simply" HTML5 pages on their website that you open in browser [1].
So what was/is happening is people see "Friskies iPad Game for Cats" they grab their iPad and search for "game for cats" on the AppStore and then they find our game and we profit.
Also, most people who have cats and iPads don't even think to look for a game for their cat. So by Friskies putting marketing into this they actually increase the size of the market (to be honest, I hope they run a TV commercial advertising their "ipad game for cats").
Moral #1 of the story is: BigCo might steal your idea, but they will likely mess it up and it can end up helping you.
Moral #2: high water raises all the boats
[1] I realized HTML5 is a "real" app, but most normals don't yet view it that way. They expect to find apps in an app store.
UPDATE: formatting