It sorta depends on if you are playing Limit or No-Limit. In NL, you can chase a straight with bad odds, because if you make it and your opponent has a hand which you don't think he'll be able to let go, then you can take his whole stack, making it well worth the call incase you hit. Generally, if you opponent has a lot of money in front of him, you can justify calling anything up to a pot sized bet to chase an open-ended straight draw, because chances are it won't be very obvious when you hit and you'll get paid off well.

A flush draw is a different story. Try not to ever chase a flush draw with bad odds, because its a lot more apparent when you hit your draw then it is with a straight.

In limit on the other hand, it is a terrible idea to chase without odds, because since the betting's fixed you don't have as much implied odds (odds that you will win more bets on later streets in case you hit).

In either case, don't ever use the 32% number for pot odds. Use the 4.5:1 that the NEXT card will complete your draw.