Will Windows 7 want two license keys if I go Bootcamp + Parallels? I read that Parallels 6+ can use Bootcamp installations of Windows, and I'd like to go this route. But I've read reports that Windows will detect a major hardware change significant enough to ask for a new product key.

Does anyone have experience with this? I'm not asking about legal issues, I'm mostly interested in how Windows will behave. With a single license for Windows, can I install it using Bootcamp, and use that installation with Parallels?
You should be able to use a single license for both Boot Camp and Parallels 6. When I set up my Mac this way, I just had to activate it twice, first booting directly into Windows 7, and again after setting up Parallels to use the Boot Camp partition. 

I think I may have actually had to activate it once again the next time I booted directly in to Windows 7, but certainly after a few activations, the activations in both environments finally stuck.