Although Matt Cutts claims that this is an algorithm change and does not involve any human review of individual websites - this is not true. They went after specific guys who sold links on their splog farms, but those who didn't are up and running. A lot of people who hired "SEO experts" were burned just because the expertise of those "experts" was buying links on said splog farms.

The thing is that google's algorithm looks like this (http://imgur.com/XxhZg) and the real "SEO experts", the black hat guys, run circles around it. If you doubt that just look at the results of your search queries. See any spam?

I've built a blog in 2005 which I basically abandoned in 2007. That blog was scraped and its content republished by a few BH guys who didn't bothered to remove links pointing to my original blog which resulted that today my blog has over 75% of its links coming from the splog farms. I'm not talking about a few links here and there. I have over 40000 of those and yet I have no warnings in GWMT and the blog ranks #1 for its main keyword.

If you're running an online business avoid hiring "SEO experts", they are not just useless they are dangerous.

So, how can you get hurt by some asshole?

First, he can buy links on the splog farms already penalized by google. Second, he can create extremely transparent splog farm and link to your site. (by transparent I mean autogen content, no keyword variations in anchor text, trackback spam, ...) Third, he can just "xrumer blast" you out of google index.

I believe that the approach google took recently will get a lot of small business (and webmasters) hurt, but it will have almost no effect on black hatters. Why? Because, with all being said and done, the only thing that really counts in SEO is the number of links and the BH guys are masters at creating those. (see: http://en.wikipedia.org/wiki/Google_bomb)

Google screwed it up big time by making negative SEO possible, but I doubt they'll change their approach. I doubt that they even care about it.