I'm a big fan of player driven events. Sometimes, though, you just need an item or two in order to give it a special touch.
I'll give an example:
Bumblebee wishes to hire a rogue or three to go retrieve a package an informant has left in Lanisport. Of course they should just RP that they get the package once in Lanisport, then return to Bumbles and RP that exchange. However, if Bumbles could request a PQ (placeable quest), then there would actually be something in Lanisport. Perhaps a chest with a sealed scroll in an upstairs bedroom somewhere. The rogues would have to sneak in and get it. Perhaps even a pair of deadly guards that need to be snuck past, or simply a trap on the chest. No GM interaction, though, beyond plopping down the placeables.
How it would work:
The PC would PM the PGM (placeable GM) withrequest, GM would make accept, reject, or request resubmit based upon feedback. The request would specify location and start time. The placeables would be there for two hours or until server reset. Server resets wipe the placeables and the request must be resubmitted. After two hours, the items may or may not be there any longer (depending on when the PGM came back to clean them up).
The PQ would have to be scheduled on the player calendar and must happen whether it becomes a PQ or not. This is because they are meant to add flavor to player quests. The quest should be able to stand on its own if no PGM is available.
Players can request PQs as often as they wish, but priority is given to players that have not had them before. These are, afterall, just player calendar quests with a chance for a few placeables.