I'm assuming the cards dealt within
Pokerstars runs off of some random number generator like that of a scientific calculator. Random number generators aren't exactly what you'd call random; they use a mathematical function to produce these "random" digits, meaning there is a big, long, list of random numbers. Assuming that
Pokerstars uses one of these devices, then we can assume that it is possible to foresee which cards will appear later, or at least generate these cards prior to their appearance.
Pokerstars could have thousands of players with direct access to the card information, knowing when to play and when not to play. Tracing these players would be incredibly hard considering it's a global network. It's the same idea as if you had X-ray vision; if you could see through the deck, wouldn't you use it to your advantage? I just don't know if you can trust a company with X-ray vision when you know their main goal is to make money.