Google is actively penalizing sites that purchased an excessive amount of unreciprocated links.
I have been told they are also scrutinizing CSS and Java scripts for artificial ranking “tricks”.
In discussing this with a few other Gambling webmasters we felt that Google may be shifting focus towards land based casinos and informational sites to the detriment of traditional online gambling portals. This remains to be seen, but there are some indictaions of this happening.