The Webmaster Central blog at Google has some useful advice for "free hosts" or websites that allow other users to create their own websites. These could include website building tools like Office Live or the various blogging services like Blogger, Tumblr, Posterous and WordPress.
We thought we’d offer up some best practices for websites that allow users to create their own websites or host users’ data, like Blogger or Google Sites. This class of websites is often referred to as freehosts, although these recommendations apply to certain "non-free" providers as well.
Among the seven recommendations that can make a free host more webmaster friendly, Blogger meets all but one of the criteria and that’s related to 301 redirects.
Someone on your service might want to change their account name or even move to another site altogether. Help them by letting them tell search engines when they move part or all of their site via the use of 301 redirect destinations.
When you move a site from Blogger to another blogging service, there’s no way for you to specify 301s and therefore you existing search ranks could go for a toss. I just hope this changes with Google coming out with an official "best practices" document for webmaster friendly web hosts.
Related Guide: Switch from Blogger to WordPress