Well, I did such an experiment a while back. Completely delete an automatic lyrics site (with very little traffic) and rebuild an auto news site. G seemed to be hesitant at first, crawling everything but not sending traffic. But after a while, it started sending traffic and growing from there, although my traffic is now halved because of some penalties or algorithm changes... not able to figure that out. The point is, you can rebuild a site with completely different URLs and theme. It works. How's your experience? Will you take the risk and build new site on old domain? Or would you prefer to register a new domain? Obviously for the latter, there are also disadvantages like new domain, sandbox, etc. Anyone with REAL experience please share so we can all learn.