It depends how adult related your blog is going to be, are there going to be pictures? If there are not and it is a textual blog, just but a disclaimer the "Content only for those 18 and above." For this, you can actually use blogger or any of the free services. But if you are going to put adult pictures and all, then put a domain and use wordpress for your blog. That way no one can ban you. At the same time, it is not the blog type that gets search engine content, it is your
SEO.
