Your online poker site has no interest in who wins or loses a pot. They collect their money regardless. You might argue that some sites might favor the "House" pros, especially in bounty tournaments, but that would be ridiculous. The bounties are normally quite low compared to the tournament fees. Seldom are they more than 5-10%, and the advertisement values is worth significantly more than that. Since these pros usually earned their position as a pro by performing well at poker, all can be expected to be more than accomplished players. When they've got a bull's eye on their forehead, they are able to play a very specific style which has a very positive expectation, and when average players modify their style of play because of the pro, the house pro gains even more advantage in the game. Additionally deep bankrolls, even if they can't outplay the average poker player, allow them to outlast most players. Of course some don't always win. Check out FullTilt on any given evening where Gus Hansen and Mike the Mouth are often losing in the high Limit Omaha games.
The second myth and probably the most widely accepted is that the miracle draws occur to increase the pot size and subsequent rake. Well the truth is more suck outs do occur, but the number is greater because the number of hands per hour online is significantly greater than in live games. An average online poker game will play twice as many hands as in the average casino game, with a center dealer, and probably three or four times as many hands than in a home poker game with out a professional dealer. Finally the online poker site makes more money when the average rake is low and the hands per hour are high. They don't want long hands with big pots. Every time the pot exceeds the maximum rake the poker site loses money. Every dollar above the maximum provides $0.00 in additional rake.
There is a reason that the maximum rake for short handed and heads up games are reduced. A short handed game completing 100 hands per hour will make more money than a full table that goes to the river every hand and only completes 40-50 hands per hour. From a shear numbers point of view the poker site would make more money if every hand ends quickly, right after the flop or turn.
So the next time you get nailed on the river, take a second and reconsider the facts before you start chatting. Suck-outs do happen. If someone else starts ranting about how this or that site is rigged, I suggest you make a note on the player to this effect: Foolish, will tend to overplay top pairs and over pairs, vulnerable to a long odds trap and might tilt.