Random????? Most assuredly not. I am not stating that poker sites are rigged either, however. I believe that the truth is actually somewhat greyer than that.
I truly believe that Pokerstars, 888 Poker, GG Poker, and other such poker sites are purposely programmed, not rigged, but flawed in their design, as to give three distinct individuals preferential advantages:
1. Larger stacks on whatever table you're playing at. This does not matter, whether it is freeroll, bounty builder, cash game, etc. It largely remains the same. Odds largely play out in the bigger stacks favor.
In real poker games, chip stacks will greatly fluctuate; big stacks sometimes go down, small ones grow large. Online poker sites, however, more often than not, seem to operate in reverse.
Very rarely indeed, have I ever seen a small stack increase in size at all, and they are routinely crushed by bigger stacks and inevitably eliminated from play. Again, this is not entirely realistic poker play (yet multiple sites claim they engage in just that, "realistic play")
2. Inexperienced players, or donkeys as they are called are also heavily favored. These are the types of players who will literally chase anything to the river, regardless of how ludicrous it seems. I have both participated in, and seen hands played, where someone (usually me) has a flush, straight, set, or even full house, and yet these other rookie players chase repeatedly, and they usually win with a marginally better hand (higher full house, straight, etc.) Also, this usually always happens on the river.
3. I am a Canadian player, and I cannot tell you of the volume of Brazilian and other foreign players I have encountered that routinely get better hands and/or runouts than I do. Again, I believe that this is something that PS's (and other sites) "random number generators" factor into the payouts and such, and accordingly allows the "rng" to operate in its flawed state.
These scenario's make sites like PS, 888 Poker, etc. very wealthy and as a result, I cannot imagine that they would change it any time soon.
So, to recap, not "rigged" but "incorrectly programmed" to such a degree that it benefits poker sites, but hinders really good players.