Here's a tale of someone who once upon a time had a blog on Blogspot and later deleted it, only to have her old blog URL taken over by a porn site. Oops.
Blogger kicked the porn people off (because they violated the Terms of Service), and the woman was able to grab back the URL. However, the general rule with free Blogger blogs is that if you delete your blog, the URL you used is made available to be used again by someone else.
Fortunately, I hung onto http://circadian-shift.blogspot.com/, and it's still there. (And still ugly. Oh well.)