As many people have pointed out, raiding guilds are starting to crack under the pressure of summer, expansion fever, and the difficulty of SWP. It seems like MH/BT guilds that are still working through that content are generally fairing better based on the comments I've read on other blogs. The difference between MH/BT and SWP is the quicker pace of progression. You actually feel like you're accomplishing things in MH/BT with new bosses being downed every couple of weeks. SWP bosses take a month or so each.
Ascent (my guild) has been rebuilding out of the ashes of other guilds. We've added 2 holy priests, 2 mages, a dps warrior, a resto druid, a warlock, and 2 resto shamans, none of which require gearing up beyond a couple of pieces. That's 36% of a raid right there. lol We're still looking to get 2 more tanks and another holy priest. Fool me once with the ninja retirements, shame on you. Fool me twice and leave me short-handed, shame on me.
There is a group of friends in the guild that have all quit raiding. Instead they've been PvP'ing and working on alts on another server. A couple of that group /gquit last night and transferred. The expectation is the rest will probably do the same. On one hand, it's a bad thing. I think the other officers were hoping once the expac hit they would come back to raid with us. They're good players, just burned out.
On the flip side, them all leaving would be good for morale. Nothing sucks more than being short-handed for a raid only to see this group playing in a BG. I also think there was a level of jealousy/resentment towards them, too. They're having fun and they're part of the reason we're not.
My own personal perspective is I'm glad they're gone. Most (not all) had this whole "I'm too cool to do that." attitude. All ranged on a mob other than the boss? Yeah, everyone but them. Must. Win. The. Meters. They would complain if they had to do something out of the ordinary, etc. It's much easier to work with the new people we've brought in. They were skilled players but their behavior was more like guild princesses.
My only concern is at some point after WotLK comes out, they'll want to return. I am currently working my butt off recruiting their replacements. These new folks aren't disposable. We want people that will stick with us. If we have valid openings, maybe. Or maybe not. Depends on the situation.