Some observers argue that the effect of the rake can make low-limit casino poker unbeatable. They reason that, if a good player can only beat a weak game for 1 BB/hr, and the rake of between $3 and $5 is taking roughly one big bet per hand out of the game, the game must be unbeatable.
Other players point to the extremely loose and weak opposition in these games. Their argument is that the same games would be beatable with two fewer limpers, or one less weak player calling to the river. According to this view, the presence of these poor players makes up for the impact of the rake. Although it's true that each additional limper reduces the "Hero's" chances of winning a pot with a strong hand, the pot equity gained by these mistaken limps is not equal to the equity added to the pot. Therefore, a somewhat more sophisticated analysis is that, while two extra limpers alone won't pay a rake of one big bet, they're probably adding enough to the pot in a low limit game to make up for the impact of the rake.
For example, suppose a certain casino offers a $2/4 game with 7 seeing most flops and a $4/8 game with 4 to the flop, each with maximum $4 rake per pot. The three extra limpers may not be adding a full $6 to the pot, because they're getting some equity from their limps. But suppose the 5th limper adds $0.50, the 6th adds $1.00, and the 7th adds $1.50. (Additional limpers tend to consume each other's live outs; consider domination theory.) The extra limpers have now added 0.75 big bets to the pot -- but the rake differential was only 0.5 BB between $2/4 and $4/8! The numbers are contrived, but the principle is that a low-limit game with many incorrect limpers will be good enough to overcome the higher incidence of the rake.