We, the bloggers, are not stupid. All your spam gets either marked as spam or deleted. And what's so great with that? It's a lose/lose situation. I'm losing time reading your spam comments and marking them as spam, and you lose your time spamming useless comments trying to get links to your blog.
Many blogs solve this problem by disabling the option to comment with a link. I think that is wrong and I always want to credit people with good comments. Some people put a few minute into writing their comments on my blog and they deserve a small reward, a link to their blog that people can follow if the comment was good and/or interesting. But the comments need to be good, related to the post and written for humans.
My blog does not have follow links on blog comments, that's why you should think twice before spamming just for the "link power" that is close to nothing. If you still want that link, write a good comment! Don't write as "good viagra" because I will just mark it as spam without reading. Comment as (example=) "Alex from ptcblog.xx" if you want to include your keywords in anchor text.
A good comment is a comment that engage people to discuss further or adds something to the topic. A comment simply saying "Good" is not a good comment. Just because this is a ptc blog, doesn't mean that I will approve all kind of crap in comments :)