aacf4497__Blogger__Tumblr_and_Posterous__0
[Blogger.com] Blogger inserts its own Navigation bar on top. Through CSS hacks you can remove it yourself. [Wordpress.com] Wordpress.com does insert some ads. Pay $29.97/year to remove them. [Tumblr] No Ads inserted. [Posterous] No Ads inserted. [0] 
Does Host Insert Ads?
Choosing a Free Blog Host - Comparing WordPress.com, Blogger, Tumblr and Posterous
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