Deleted blogs get "hijacked".
03/03/2007. If you delete your blog on a publicly hosted blog service (such as blogspot.com), and not just delete the entries but delete it entirely, it's likely that some other individual or organization will re-register a blog with the same URL, and use it to point to their spam or "ad farm" web site.
They do this because many other websites/blogs have linked to your blog, and they (the ad farmers) want to profit from your old score/ranking on search engines. And they hope to get ad revenue from people who follow the "old" links to your blog.
Moreover, if a highly ranked website/blog links to you, then that incoming link scores even more points in ranking your website/blog.
An axample of this was the blog "Must Love Books" aka "Someday Saint", which was given links at a multitude of other blogs, including popular ones TimesAndSeasons.org and MillennialStar.org.
When the "Must Love Books" (Someday Saint) blog was deleted, someone went to Blogger.com and registered/reserved the same URL (someday-saint.blogspot.com), and used it to point to an ad farm.
If you have a blog, and want to delete it, I would suggest deleting the entries, but keep the blog URL. Or if you put up a new blog somewhere, post an entry on your blog directing people to the new blog. If you want to totally wipe out your old blog, delete it, but register/reserve it again, so it remains empty. Hopefully, that will avoid the frustration of people following links to your blog only to be disappointed with a bunch of crass ads.