This is something I've always wanted to do. I've never made an online game before but this seems like a good place to start. I like the purist feel of text-based games, and the mechanics of many players interacting has always fascinated me.
In almost all TBMMOs there is very simplistic and boring gameplay: click a button to perform an action, wait two minutes, click again. Bootleggers.us is the most entertaining one I've played. While it does have click and wait elements, it also has other features that are far more enjoyable and interesting.
There is a trading element to the game - given the theme this involves smuggling alcohol - where items are priced differently in different locations. Prices fluctuate based on stock levels affected by players selling or buying. This is a nice aspect to the game which requires the player to research prices and plan their trade routes.
There is a market where players can sell their items (weapons, cars, protection). The market is very interesting because players price their own goods, so the market can boom and crash depending on how sellers react to current prices. There are independent markets for each location, this adds another level of strategy as one location may have very different prices to another.
Organised Crimes are the mainstay of the game, they require one player to recruit several others to attempt a bank robbery - the result of the OC is calculated using the players' ranks and the quality of their equipment. This kind of recruitment game play is surprisingly lacking from most Text MMOs I've played.
A nice side-feature in Bootleggers is the Escrow option, where two players can trade items by agreeing on the terms beforehand to avoid any foul play. This feature should surely be included in every MMO.
What Text MMOs have you played? What interesting features do they have that go beyond the boring click and wait system?