If he has a business plan that he and his investors feel confident in, he has the drive and determination, and he finds it fun, I say go for it. Of course, he could also sell and sink the cash into another venture, so he has less reliance on venture capital. Depends on how he feels about how far he can carry his technology versus come up with new ideas.
Personally, without having seen it, I think it's dangerous to turn down a boatload of cash for something that can get kicked out from underneath you pretty quickly. Of course, I'm not so brilliant Facebook is offering me millions, either.