There are reports that BlackBerry Internet Service, which is sort of a portal monitored by RIM (so it's not carrier-specific) through which BlackBerry data runs, is down worldwide. That could affect email, BlackBerry Messenger, web browsing and maps, to start.
According to comments on various message boards, BlackBerry data is either out or patchy at least in the States and Canada, with users unable to access BlackBerry services — but not necessarily third-party software like Opera Mini or Google Maps, although some, like Facebook, use BIS and are thus having problems. It's not carrier-specific, with problems being reported on Verizon, T-Mobile, Telus and Rogers, but it's also not universally down like the Great Sidekick Outage of 2009 — some users are reporting no problems at all, while others are completely unable to access data. We'll keep you updated, but in turn, why don't you keep us updated: Any BlackBerry users out there having data problems?