Firstly, from a hacking standpoint, I'm not concerned about it because I have everything beyond the first two ranks restricted by authenticator. People cannot be promoted beyond Initiate without one, and all an initiate can do in my guild is 10g of repair a day and see the bank contents (but not access them). When people get beyond a certain point of inactivity, I demote them below the initiate level to inactive, which has access to nothing but guild chat anyway.

Secondly, I don't consider my guild a business. The core of the guild is made up of a group of people who've known each other for ten years, and most of the people we invite are people who revolve in our various circles both in and out of game. I'm not trying to pad the numbers, but when people leave the game, I feel a certain amount of camaraderie with them, and I see no reason in kicking people I consider to be my friends from the guild. I communicate with many of them out of game through other channels, e-mail, AIM, or Facebook.

And yes, while we all know that as long as you rejoin the guild you left you won't lose any ranks or perks unless you joined another guild in the interim, maybe the average player doesn't realize that, and will simply go join another guild when they realize they've been kicked out of the one they were in. I'd rather not make it harder on someone coming back to the game after a hiatus to get their bearings. I took a break for a period of a little over a year during BC and early Wrath and coming back to everything being new was bad enough without having to worry about why I wasn't in a guild, trying to find someone online from my guild to reinvite me, etc.

Looking at my guild roster is something like looking at a yearbook. It's fun to look back and see the people who used to be around a lot, even if they aren't there anymore. It's a little snapshot of guild history. To each their own.