May be it's not so difficult to deal with those thousands kinds of different spammy comments for google, but as clever google, it knows even can kick these spammy comments out, there will be so many ways to cheat in seo still. Besides, anti-spammy-comments is the problem those blog service providers should deal with, after all, those low pr backlinks are not so important in Google count methods, so... there is no attractive enough reason can make google work harder on spammy comments.
It is to hard to tell spam or not spam, what if there's 2 comments on different blogs one of it looks like spam while other does not. What decision will make G ?
it is impossible to effectively monitor comment spamming and that's why google created do follow links, so that website owners can decide whether or not to give link juice to a comment.
They have way more success combatting spam with dofollow links and using authority as a key ranking factor. That's why you can put up a new domain and drop a few thousand spammy links and get nowhere but use a parasite host and start getting traffic right away.
you should be cautious about google, they can do anything, from finding out click fraud to comment spamming.
google is a big ball of mathematical algorithms and as such, I think there are far too many unrealistic variables for it to achieve. This being one of them. It's like link acquisition rates - so it's your fault if you have 100,000,000 people wanting to link into your site because you have good content? ridiculous....they wouldnt penalise you for that....\
Exactly. People assume they're being penalized when in fact they've just neglected every other factor. In my opinion, tons of spammy links can start to work in your favor once you've got some good ones in there. That's just speculation though. I don't know if it's that or that a small portion of those spammy links are from authoritative sites.
Sites must be relevant or related to your site. My sites rank well for many keywords and a lot of them are from nofollow blog comments.