Like everything else about Poker, it depends, it depends, it depends. If you're playing full ring, then there's no reason to ever play (2,7-o) unless you're making an advertising play to shake a nitty image, or you're just plain stealing where your cards don't matter. (2,7-o) can't make a straight, it makes underpairs, and needs to hit two pair or a Full to be worth anything, and those are long shot flops.
Different story when playing head-up. The 7 is good mid-card strength, kickers are less likely to be a factor, and 2nd button stands a better chance of winning. In SB v BB situations (2,7) in the SB isn't a bad hand to hit it. You just might pick up the BB, and if he calls, he may not be able to beat your pair of 7's. You see a flop like (A,7,2) (K,7,2) (Q,7,2) and he has the TP, you just might stack him. Flops like that look very non-threatening to TP, especially in a HU or SB v BB contest. It's especially nice if he figures you'd never play a (7,2-o) because "everybody knows" it's the worst hand.