Lately I've been braving the 40min random heroic queues and finding myself in a group with 3-4 people from the same guild. I always find it interesting to see how these guilds handle themselves, because like most PuGs, some are great, some not.
Example: Guild #1
I entered the PuG and found myself with 4 people from the same guild. Nothing was said in party chat. As soon as we were standing in front of the first boss - kicked. No explanation, of course, but since they hadn't had a chance to properly assess my DPS and we hadn't wiped on all the trash prior, I'm going to assume they kicked me for a guildmate.
Example: Guild #2
I entered the PuG and found myself with 3 people from the same guild. Very little was said in party chat. During the course of the dungeon, we wiped several times on each boss, occasionally losing the other PuG DPS and gaining a new one. On the last boss, we finally got a PuG boomkin that stayed... and spent probably an hour wiping, although it was clear that we were improving each time. Occasionally someone would suggest something to help.
At this point, I had expected that the 3 guildies were sticking it out because they hadn't done the dungeon; I'd been in a couple of groups where guildies left after a couple of wipes and we'd been in the dungeon for almost 3hrs. To my surprise, when the boss finally went down the only people that had Achievements dinging were the boomkin and myself - those 3 had wiped repeatedly, offered suggestions, put down repair bots and changed boss strats just for us!
Of course, whenever I'm in a guild group and we pick up a PuG or two, I always feel sorry for the PuG(s) when we wipe... so perhaps I'm just being hard on myself to not fail a group, even when the fail isn't my fault.
Still, it's nice to come across some really decent people in PuGs now and then - it makes the run seem that much better, even if I have a huge repair bill and nothing but a few JPs to show for it.