Well, Dario, it was actually someone at WMF. But I don't think that should matter much. Let's do this as a compromise:
If someone runs an hourly report longer than a month and a daily report longer than a year, we give them a warning telling them what's going to happen. If they say OK, we have to assume they know what they're doing and they really need the data.
I know I accidentally ran a really long query once, so we'd at least guard against that. Like I said though, even that crazy long query last night didn't cause any huge problems. It just used up a bit of memory and slowed access to the wikimetrics server for a few hours. There are a couple of simple monitoring, tracing, and backup improvements I could make in order to alleviate that as well. So if it keeps happening despite the warning, I'll just do that.
Dan