Google has a really enlightened guy called the Data Liberation Front. His role is to make it easy for people to get their data out of Google - rather than it being locked in.
Usually, people are locked in by the lack of an export feature, or an obscure file format. In mapping, people are locked in by licences.
Google could fix this by saying that tracing from their imagery is ok - just like Yahoo have done. On my blog, I looked into the legalities of this and concluded there's nothing in law stopping them from doing so. It's entirely their decision.
So - please vote for the Data Liberation Front to fix this! Click here, sign in with a Google Account, and tick the box. And tell your friends.