In the beginning of Planet Mule, players would have to wait hours sometimes until those few players able to host a game were available to do so. Once game was filled, the remaining would just twiddle their thumbs till a game became available. A few users would try be generous enough to open a game and host for otehrs even if they didnt want to play, but even then it was still hard to get a game.
When Mainstream introduced the automated hosting bots Mule4u/Mule4u2/mule4u3, things changed immediately. For first time, we now had had constantly available hosting options, and therefore it became much easier to have a game. I think there were 3 bots in total, although all 3 were not always available, but at least one would usually be.
Planet Mule growth would have been much harder without it for sure.
Anyway, mainstream is now releasing the software so that others can now host the bot software. Hopefully this will mean even more bots, and it being even easier to get a game.
http://www.planetmule.com/forum?topic=1844.0