I recently read an article in the Writing for Dollars newsletter:
7 Reasons Why Your Novel Needs a Book Proposal
by Patricia L. Fry
http://www.writingfordollars.com/2007/vol11num17.html
Yes, a proposal, not a synopsis, which would be part of the proposal, but a full proposal.
I’ve written non-fiction book proposals, they require a lot of research. Off the top of my head, I can think of one publisher who requires a proposal as part of their submission package for a novel, but I’m sure there are others.
Perhaps proposals are the wave of the future?