freejung - 10:54 pm on Jan 14, 2011 (gmt 0)

I went through this a couple of years ago in my day job when we acquired a new product that was only tangentially related to the business we'd been doing for more than a decade. It took a while for Google to sort it out, but we didn't have a lot to lose because we didn't have a lot of search traffic at that time anyway. We've added a lot of great content and got a lot of great links since then, and we're doing much better, but I still think the dual-themed-ness of our site is holding us back and if I had it to do again I would strongly recommend just starting another domain for the new product.