Don't ever use the expression "last time I checked" when referring to something obvious, well-known, or widely believed. You come off sounding both arrogant (it's a bit of a sarcastic dismissal) and dumbly folksy (it's vaguely self-deprecating--sort of). I see it in discussions, blogs, and sportswriting. It's simply far, far too overused, and therefore should be avoided.
Jason Ivanitz of the Crookston Daily Times (Up North Rube Cred) writes: "Last time I checked, sports were about teamwork and all coming together for a common goal."
The Betting Fool of the San Francisco Chronicle writes: "Last time I checked, a closer's 'job' is to close games, not lose them."
Mark Soltau of Golf Digest.com writes: "Last time I checked, this was a golf tournament, not an audition for the toughest U.S. Open course in the event's 107-year history."
Adam Schein of Fox Sports writes: "That's the organization known in circles as America's Team last time I checked." I think it is also Schein's response in a mailbag here: "Last time I checked, you didn't have to play football to have an educated opinion on it."
Anthony Arroyo of the Journal-Advocate writes: "Sure, you may say 'it’s only Arizona,' but that same Arizona team does lead the National League West, last time I checked."
Jim Reeves of the Star Telegram writes: "Those of us who live in glass houses--and last time I checked, that just about covers most of us--shouldn't even think about picking up a stone."
The way it looks, everybody is doing a lot of checking, and they're making sure to reference the last time they checked.