When patch 3.0.2 hit, we had a very long maintenance, shading towards 24 hours for some realms. And since then we haven't always had the best of realm stability; I know my own realm has had plenty of restarts, downed instance servers, and lag spikes in the past few weeks. It would have made raiding pretty hard if they hadn't nerfed the pants off it.
Blizzard knows about the realm problems as well as anybody, and as is their tendency, they're compensating for it by giving us all playtime credits. This time it's a full three days, for anyone with an active account on US, Oceanic, Latin American, European, and Russian realms (so basically everyone except Asia; the Asian realms have a different payment structure).
That's one thing I really like about Blizzard. They may mess up, but at least they try to fix it. Now can I have a Squashling, please?