I agree with Kitsune, in a way. It seems every time I go to advertise in Fluorite Plains, I end up seeing at least two or three other groups that are basically offering the same thing I am. It then becomes a competition of who can get the players to their side. And in contrast, there are times when there are no advertisements at all in general, and one gets swamped with those are itching to join, and no where to go.
Socklet.
The only problem I see with advertising when ever the active group count gets low, is keeping track of them all. And in retrospect, I'd simply be adding more and more people to an active-watch. Our roleplay is plot-centered, as we're going towards a certain goal and so it's hard to introduce new members that frequently. Though, I suppose like you said, that could only add to the plot.
The forum, though we have one, and a number of our members use it or check it at least once a week or so, the only problem with that is, I've noticed a number of people will sign up for it, and then never come back to check it. They do it simply to get the map, and then it's game over for the forum. I attempt to make timezone friendly events, however it is hard to do with the combined schedule of all the members, and so I've used a poll in the past to pick an ideal day, and such, etc. The time is the problem most people need to be able to hammer.
In which case, I believe I would have to limit my member's nationality, in order for the roleplay to be more organized and correlated. as much as I would hate to do that, it is something I am considering for the next time I advertise.
I agree with you in that jumping around roleplays to get acquaintances is a good idea, and I've gained members that way in the past, however it's finding the time to actually go through the process of snatching them away that I find tedious.
Another thing I thought of, sparked by what Kitsune said, how she leaves when she feels the odd one out. People tend to leave if they're "bored" during roleplay, however, they complain that no one is interacting with them, when they themselves are doing nothing to interact with anyone else. When I join a roleplay, I usually sit around until there is actually no reason for me to do be there, if all the members have left, or gone offline, because I believe it's rude to the leader, to leave because I grow bored; I leave when I'm needed in my own roleplay, and even then, I ask if they mind me leaving. I could just be too considerate though.