Like Darko123 said, this method has been around for awhile.
I’m always suprised that people want to quickly label any “innovative” approach as blackhat, or spam or whatever. Anyone who engages in active link building rather than passively letting their sites get natural, unsolicited links is in fact gaming the search engines according to their terms of service.
If these counter links were not hidden would you still consider this technique blackhat? My guess is many would.
The problem is not with webmasters but with how search engines value and ranks sites.
As long as links hold so much weight webmasters will be looking for ways to build links with the greatest ease and speed and I don’t see this changing until the search engines themselves change.
Since we are all really operating in a grey/black area with respect to link building I’m not too worried about what other people do unless it directly disrupts other peoples sites like blog spam, forum spam etc.