WOW has some problems with groups. One of the big ones is that groups tend to have fixed structures in terms of roles, and the other is that groups are only generally successful when they have some people involved that are overgeared for the content. It is possible to win with bad role balance or poor gear but it tends to take practice and patience and so it rarely happens in PUGs.
Role balance pretty much boils down to there not being enough tanks. Everybody can do damage, and many people can only do damage, so there is always a shortage of people wanting to tank. Tanks also have the responsibility of deciding which mobs to pull, how to physically arrange the pull, and are generally assumed to be in a leadership position, and that responsibility drives people away. For quite some time now Blizzard has bribed tanks to join up in the LFG tool to try to balance things out. At the moment they are offering 200 gold and an item that can be handed off to another character on the account to get tanks to queue up. I have seen people complaining about how tanks get such juicy rewards, usually something along the lines of "But my class can't tank, it isn't fair that tanks get stuff for free!"
On one hand it does seem unfair that some classes have options to make tons of cash while they get to instantly join up with groups and others do not, but overall the experience for everyone is way better with this system in place. Without it dps classes just get to sit around for an hour or more waiting for a tank to show up and that isn't fun for them at all. Better a little inequality than a worse experience all around.
Recently I have been PUGging heroic raids and I notice that an awful lot of them had specific items 'on reserve'. This means that the raid leader (or their friend, presumably) will automatically take the item if it drops. At the outset I was really pissed off by this behaviour and resolved to not join such groups, but eventually I noticed that although it was bothersome in theory in practice it seemed pretty fair. Those people reserving gear were usually overgeared for the content and only needed one or two drops in the entire zone. They were usually doing top damage and had a lot of responsibility in describing mechanics, making groups, and even just showing up first to wait for everyone to join. If all it takes to get an overgeared, experienced person to lead the raid is giving them a single item while everyone else gets to roll on the rest, isn't that well worth it to the group?
Of course there always exists the possibility that a leader is undergeared, incompetent, and/or greedy and they don't bring much to the group to justify the reserved gear. In those cases though I think the group generally accomplishes very little and often doesn't get off the ground at all. I know I will never join a group with gear on reserve unless the folks getting it are otherwise geared to the nuts so this problem likely fixes itself fairly quickly. I suspect that most of the time the people doing the reserving are actually in a reasonable position to do so.
What I was also mulling over though was what exactly this does to raid comp. If I see a bunch of PUG groups listed and one has a piece of plate on reserve, should I join that group? Seeing that probably means that other platewearers are likely to stay away, which is great for me, and it also means that all the other plate in the zone in unlikely to be desired by the leader. It does seem bizarre that a group with plate pieces reserved for someone else would attract me to it, but that actually seem like how it shakes out. I wish I could find data on how that works in general though - how do random players respond to gear of their type being reserved? Clearly if that is the only piece they need they stay away, but what if they need a bunch of pieces including that one? Do they stay away anyhow?
I do know that I am far more likely to get loot in a group that kills a bunch of bosses regardless of whether or not there is a piece on reserve and I suspect other players feel the same way. Though it may not seem exactly fair to reserve loot, I think the rational response to people reserving loot is to require them to be awesome enough to warrant it and then just accept it and move on.