Below is a picture of my personal chart that shows the problem with rake for my game.
Over the last 50k or so hands, I won about $1500 paid roughly $1380 in rake and won about $120. This is 50nl, the first 20k hands is FR the rest 6max.
If you also think about my "playing pleasure" you will see that there is a long stretch of a slow downswing after the 20k hand mark. This is where I switched from FR to 6max and there is probably somewhat of a learning curve happening. The critical part to note here is that I actually won but because of the rake I ended up losing slowly. Slowly winning instead of winning is a big difference when it comes to playing pleasure.
The site of course should be quite happy. They make about 10x the money they actually move.