depends what you're goal is. If it's a one-run ballgame and Ortiz is leading off an inning, I'll take that .500 bunting average (which is probably better against the shift). If he fails on the first attempt, then let him swing away. The only way it's a bad move is if Ortiz lays down a sh*tty bunt right back to the pitcher, which is possible, but unlikely. If he's aiming up the line, it'll either be a good bunt or go foul. Are those the only two possible outcomes? No, but by far the two most likely.

What makes you think a bad bunt would be unlikely?  I think it's at least equally likely (as a good bunt), if not more.

I still say taking the bat out of his hands in the hope of a bunt single is a bad idea.  If it's a close game, you're probably better off hoping for a HR.

How often do HR occur? I'd much rather have the leadoff guy standing on first base, with opportunities to manufacture the run or have others hit him around. HR's are nice and pretty and all - but they just don't happen that often.

Yeah but Ortiz already gets on 38% of the time.  His HR rate is over 5%.  His double rate is is over 6%.  You're completely giving those up for a small increase in OBP* (along with the added WP of an extra base hit over a single).

*Increasing OBP from .379 to .500 is not small, but I'm guessing that as Ortiz bunted more, his success rate would fall from 50%. 

It depends on where you are in the game.  If it's early, then you want to bunt away.  If they're going to give you first base in the early innings, take it.  Every time.  This may discourage the defense from putting on the shift in the first place in the early innings of the ball game.  It may also force them to think twice about it later in the game.

Late in the game, if you need the double or need the home run, then you swing away despite the shift.

OBP of .500 seems pretty good.   I guess we're also assuming he'd never walk while planning to bunt.    That seems wrong, if he can lay down a ****** bunt back to the pitcher or put one down that rolls foul, I'd imagine he could take a pitch that's out of the strike zone.