Last week's episode of STOked discussed a controversy in the Star Trek Online surrounding scheduled content. The game has recently added some much desired additional group content, but this content has only been available at specific times through the game's event calendar.
The community seems quick to point the finger at Perfect World and the game's new free-to-play model. This may be true, but it is at best an indirect effect. Nothing in these minievents that I am aware of requires purchases in the cash shop. Rather, the time schedule may be a legitimate attempt to help players enjoy the game - where perhaps eventually someday they might spend money.
If you let players pick and choose their own groups, the folks with guilds will do the content they want to do, and everyone else will be stuck waiting because there is no one piece of content that everyone can agree to run. Where most MMO's focus the random group pool by offering rewards for agreeing to run random content in the interest of forming groups faster, the scheduled content approach focuses the pool by saying that the one event is what's available at this time.
In some ways, the approach is a stick (no access to content if it's not the right time) rather than a carrot (reward for agreeing to run a random dungeon). However, when you look at the effects of the random system, every piece of content in games that use it now has to be designed to be easily beaten by a PUG of potentially dubious composition. Setting aside a specific subset of content and saying that this is the stuff that any five warm bodies can clear for rewards may have less overall effect on the state of the game.
In that case, though, the solution is as simple as it is elusive - make more content so that this one mechanic is not getting all of the limited new stuff that is being added to the game.