What I've been thinking is that trying to design gameplay that is fun for the hundreds and hundred of hours (or whatever long time) that a mmorpg or PBBG (persistant browser based game) is almost insane...but even more so, it misses the point really.
These games go on for a long time, real life days atleast. Any activity done for that long gets boring. You essentially can't have a game who's moment to moment gameplay is fun for hundreds of hours involve, like an average mmorpg has.
There's really no point. Or to be more exact I think about how I want to play and I think I would rather just collect currency while offline than play something until it bored me to tears. Each is bad, but the latter is worse. Keep in mind collecting currency while offline already happens to a large degree with auction houses and how someone might just log in to check how their auctions have gone.
Maybe it's possible to make a game that's fun to play for hundreds of hours (when your a solo designer with a limited amount of PHP knowledge). But I'll just conclude it isn't and move on to the idea of offline currency gathering, with optional extra play.