Now that Twitter has bought Posterous, and they will likely shut it down at some point, it makes sense to think about moving my blog to another service.<p>If I have a Posterous blog on a custom domain, and it has a certain Google page rank, if I move the blog to another service and keep the custom domain, I assume that the Google page rank will remain the same.<p>Is this correct? Is there anything I need to be careful about during the transition, so as not to get a lower rank in search results?