I wouldn't mind at all.Imho any new mechanic/content added that players would enjoy is fine by me.
In saying I'd never play them, mainly because I can't commit the time or "scheduling" play-style that seems to come with the raiding mechanic.Meeting at a scheduled time in-game to do a task that may take up to several hours just doesn't adhere with my lifestyle.I also don't like being placed in situations where if I have to leave the game for any reason I may put my team at a disadvantage or risk of wiping/losing.
It also isn't really why I play games like GW2 either.I like to log in do a few things either solo or with friends/guildies and then bid my farewell at my convenience without stuffing up anything they are up to.I'm sure many of the people I've met in this game feel the same way.That could change dramatically if every time I logged half my guild and friends were locked into raids that take hours.I think this possible effect on the community and social dynamic also has to be taken into account.
It could be hugely counter-productive to the games appeal to the already established majority, which as mentioned by others can be viewed as "casual" although I don't think that's really accurate as opposed to players that just don't won't to be made to feel forced or "locked" in to playing for several hours consecutively to attain a goal.
As such while I have no initial objections to such a mechanic being added it would most definitely have to be implemented in a manner not seen in other games so any unforeseen issues didn't bleed across into the rest of the game.
I pretty much think it will always be something that is found, and should really be looked for, in other MMO's.I don't realistically ever expect it to be added.