Electronic Arts sued - plaintiff claims they stole his idea
Techdirt reports that EA has been sued by an individual who claims one of their games came from an idea he presented to them. EA denies this was the case. The Techdirt post does a good job of explaining why there should be no ownership of such an "idea".
From a legal perspective, the only way to make claim to an "idea" is to patent it, or to show some sort of confidentiality breach.
It is not unusual for individuals to come up with an idea they think is valuable that they want to pitch to a business - thinking that their idea will be worth something. As Techdirt points out, you can't blame many companies for refusing to sign any sort of confidentiality agreement in such cases. They are concerned that doing so would limit their ability to use the idea even if they came up with it independently.