I would say yes but then again, i am spamming as we speak. So, I would like to revisit my answer to: "No, it's a way of identifying the author" ;-)
But then again, the "nofollow" rule is active.

Yes it's spam if you're pointing to a deep inner page of your site.

No it's not if it's pointed at your home page or blog.

A clear indication of comment spam, even if the comment adds value to the conversation, is when it is obvious the commenter is using anchor text that is not that name and pointing to a page on the same subject. These I always change back to name of commenter.

I think it's all in the context and presentation. Some links within comments actually do make sense, are relevant and improve the dialog. Others, like the "Nice post, click here!" type, are crappy and spammy. It's all up to the blog moderator to decide. Even though the majority of the blogs out there use "nofollows" on their comments, you still don't want spam everywhere.

I like seeing the link in comments. If the comment is well presented and articulate, I may click through to the authors site.

Adding your link is not solely a spam tactic.

A good hyperlink in a comment references an outside source so that the reader can learn more if desired. If you think readers can (honestly) learn more from visiting your web site, then post a link to your site.

The 'Posted by' name/link is useful to me in better identifying the author of the comment. It gives me the ability to learn more about or maybe contact the person.

You can utilize the nofollow attribute on your links if you want to ward away comments who's sole purpose is to build inbound links to a web site. I would expect a decrease in comments as a result, but it may be a good thing if you value quality over quantity.

Spam could be simply stated as forcing content on someone who did not request it. On a blog, they are setup to encourage interaction with the subject matter.

Those who contribute to the blog by providing valuable content are contributing content in the appropriate environment. So crediting your contribution is not spam.

Putting a comment about cheap band t-shirts on a site about iPhones would obviously be spam. Adding no value to a thread and then putting a link would also be spam.

But I believe contributing something of value and leaving your "electronic signature" so to speak is not spam.

Definitely agree with Matt Bee (at least on his second thought!). There's something to be said for knowing who's commenting. Sometimes comment sections and forums and the like can get catty or worse behind people that choose to hide in anonymity. Not that anonymity doesn't have its virtues at times, but it seems more often to be used as a way to write stuff you would never admit to saying to anyone.

There are definitely people who take advantage of forums just to get links. But I think for most people, a forum is a great way to communicate and learn about their industry.

Most blogs I thought had or will have a no-follow so why would anyone choose to waist precious time spamming the blogs.

Blogs and forums are there for the world to learn from each other through communication.

As soon as there are too many spam links people will close the blog and go elsewere.

Wishing everyone an exseollent 2008

One can often see very blatant coment span on blogs, from sites that quite often are totally unrelated to the general blog content. Higher quality, well moderated, more niche blogs generally have higher quality content from proper authors, who deserve the links for their efforts in growing the knowledge base of their community.

What is spam. I don't get it

Who are we kidding; website owners obviously wan to post their links wherever possible. The only thing we can do is try to do it tastefully!

I don't believe search engines are smart enough.