1. How can you have a stable clan community with out its membership being set to a certain standard.
What are these standards.....?
That is the question.
1. Honesty.
2. Loyalty.
3. Sportsmanship.
4. Communication.
5. Friendliness (The last does not matter as long as the first four are met.)
Don't ask if you cant tell and notice not one of those asks it members to be active.
Clan hopping is still prevalent..sad. 
I have a different take.
The onus is on the clan to provide the following in a competitive environment:
a. fun - if it isn't fun, why stay? This is a game.
b. activity - if my clan does not have something going on I can't expect people to want to be a part of it.
c. standards of behavior - in order to have fun members need to not infringe on other member's rights or the rights of those out of the clan.
d. communication - clan members should have at least one solid way to get in touch and talk. Multiple ones are preferred. Forums, irc, vent, all give different levels of interaction.
That doesn't mean that members should be hopping all the time. Friendship and loyalty should matter.
But we have to realize that for some competition is what they are looking for. They may want a clan that not only is good but that is frequently active to show how good they are. Those who want this competition are going to go where they think they will be valued most. In many respects the free agency model and glorification model for sports figures has played into this. Some consider themselves a big talent, and want to be in whatever clan will showcase that. For those who take this view they will look for clans with the same mentality.
Clans without this mentality need to identify these folks and steer clear of them. Or if they are already members encourage them to move on. Dissatisfaction with the climate of a clan will just fester and may bother others unnecessarily. It is better to encourage the person to move on and pursue their true goal.
Some may also take time to find where they fit. For these clan hopping is just trying out options.
There should be loyalty. But this is still a game, not a marriage. And if the clan does not provide what the members are looking for they will move on.
Rather than lament the disloyalty of members we need to focus on the responsibility of clan leaders. Good organizations and good leaders inspire loyalty--not demand it.
At this point our clan has built-in disloyalty. We are a training clan. We expect people to move on. But it is still good to hear that often times they miss the clan experience or the people, or some choose to stay regardless of an offer.
And I am sure GT has had similar experiences in its long history. But you, and I, and all clan leaders, need to ask as a leader what are we doing to serve our members? And if they are leaving, why are they leaving?
Any organization and any leader must insist on such self-evaluation.
I don't pretend to know the facts in JpKool leaving, and I think your topic goes beyond his case anyway.
Loyalty is a fading value. It is something that should be encouraged. But we can deal with reality in the current climate or we can pack it in. That is the choice of any organization.
Now having said all of that, I have seen some folks who have two lines of clans listed, some for only a day. That is a reflection on their stability. I would not be in a hurry to take them in as a leader.
