Argument from lack of imagination. But I don't think the the large, well-represented adversarial client is as common as the clients who are simply stupid. Either way it's not something I have a lot of personal experience with, but Clients from Hell is pretty full up with stupid, greedy clients and equally stupid designers with bad contracts. As an example:
http://clientsfromhell.net/post/107004953453/me-your-invoice...The above is clearly a situation where contract verbiage for transfer of rights would make any subsequent conversation on the topic very short. However, as to your general point, what do you suggest? Is that risk something that can be mitigated, or priced into your rates?