DWhatley is the only non-pro I can think of right now, unless you count the folks raising babies, but Carol has sometimes, and probably a few others. And a lot of the researchers and pro aquarists, like Jean, Roy, Marinebio_guy, and gjbarord, keep a lot of animals at once. I know Thales has a bunch of tanks linked together for filtration, and while I don't remember him having two octos, he's certainly had one octo and several tanks of cuttles. Just to reiterate (for people searching this thread in the future) two octos in the same tank often causes problems ranging from undue stress to cannibalism.
edit: due to brain failure, I forgot Dreadhead had 2 octos in separate tanks until yesterday (

) and AM had one at home and one at work recently. Sorry for forgetting you guys.