In most Strat-O-Matic Online player sets, we remove cards from play that we feel are Flukes - i.e. cards that are too strong compared to the players' expected career performance level, by virtue of the cards being based on a small sample size (few PA or IP).
One example is the 2009 card of Randy Ruiz (.313/.385/.635 in 130 PA) - if we allowed him to play a full season in SOM Online, he may very well lead the league in homeruns, which is not believable by any stretch of the imagination.
Of course that's a fairly extreme example, and there are plenty of borderline cases that sit on the fence between acceptable and "too flukey". And, since we are making what are basically judgment calls, we are bound to make cuts that may be unpopular, unintuitive, or even (in hindsight) regrettable. However, the vast majority of cuts are for reasons that are defensible, and we feel that such an approach is worth it overall, compared to the alternatives.
The alternative of making no cuts is not feasible, for the basic reason stated above (although see below for a solution to this...).
The alternative of defining hard guidelines for whom to cut and whom to keep does eliminate uncertainty of expectations, and arguments on a card-by-card basis, but its drawbacks are too severe. First of all, it would be too hard to define fair guidelines because there's no basic metric to determine how "flukey" a card is, and even if there were it would have to change from year to year because statistical norms change over time. Second, strict guidelines would cut many seemingly acceptable cards unnecessarily. Third, no matter how clear our posted guidelines are, managers are going to complain about their favorite player being cut anyway. In fact, in addition to the complaints about certain cuts made, there'd be complaints about how the guidelines were determined!
In conclusion, while it's noble to remove subjectivity out of the equation, it's worth the (in our opinion) slight unpredictability to make for what are (in our opinion) better decisions, and a better game.
However, for the first time, with the launch of the 2009 season set, we are offering what may be the best of all worlds - an alternate, selectable 2009 set that includes all the Fluke cards omitted from the default set. So if you want to play with ALL the cards, flukey 50-AB seasons and all, now you can.