Mark em as a donk. I'm sure there are other holes in their game you can earn some chips off of. Personally, I will make some small bets if I think I have a better hand then the other big stack. I simply don't want to miss an opportunity to earn chips. Or I could potentially try and steal if the side pot is more than the chips I have invested. As far as being a -EV strategy, I find it easier to build my stack by playing more people with shorter stacks then having fewer players still remaining with larger stacks.