It's funny actually -- twice I've been at big investment banks, where a trader/analyst has come on from another place and brought screen shots with him from his old job. "This is what I want, and I assume you guys are competent to create it." I think it kind of skirts the line on IP, because none of the ideas are completely novel, and the implementation is from scratch. But sometimes knowing what to build is harder than knowing how to.
I've seen this too. I used to think it was surprising. But now I realize it must have happened so many times at all the major banks that even if one of them thought they could sue another and win they would be opening the floodgates to an unknown number of counter-suits. So I think that's why everyone quietly ignores it.