How long to pitch before disaster?

With the average middle of the road sanitation, how long can wort go before pitching yeast? Is there a rule of thumb that for example "after 12 hours chances for infection go up dramatically"...What do the experts here have to say?

I don't know if there's a theoretical maximum or anything, but I've waited overnight for maybe 10 hours or so (to let the wort cool down) without any problems.

I probably should mention that that was in an ale pail sanitized w/ star san. If you do a search for "no chill brewing", you can find a whole bunch of stuff. Basically, they transfer boiling wort to a heat-resistant plastic container and leave it alone for essentially as long as they want.

I know of no-chill brewers that let their beer sit for weeks before pitching. But, of course, they sanitize the cube with the nearly-boiling wort itself, which is probably more effective than sanitizing cold with chemicals.

The longest I've waited was less than 24 hours, when I needed to cool a lager down from ~100 degrees to 50ish in an ice bath (with limited ice on hand).

I'm not sure what 'average middle of the road sanitation' is, but I've had corny kegs (sealed and well sanitized IMO) of wort that I no-chilled and left in the ferm chamber (to get down to pitching temps) for a week that were fine, and I've forgotten a bucket of spent grains in a hot garage that smelled like a dead body after two days.
Summary: depending on sanitation, YMMV greatly.

Look up the threads on no-chill brewing...

Also, aside from the hops, aerated wort is a delicious and near perfect bacterial medium. One of the goals of your yeast, aside from the obvious, is to outcompete the bacteria and other wild yeast, depriving possible bacteria/yeast that may have landed in your wort since coming down from boiling temps of O2 and sugars (maltose, dextrose or whatever else you used to make your brew). If your sanitation was spotless and your equipment was sterile before you added your wort then you should be okay... But it's hard in a home environment to absolutely ensure that so you may have some bacteria in or around your vessel. So overnight or even 24-48 hours MAY be okay... the no chill guys do that all the time... I'm just too paranoid and try to pitch at the end of the brew session... REgardless, everyone would agree that sanitization and good sanitization practice is so key for good beer.

Good luck!

I've gone 30 hours at the longest. At Hop Madness this year, I brewed and chilled (like normal) a fresh hop amber on Saturday, and wasn't able to pitch yeast until I made the 2.5 hour drive home on late Sunday. Beer turned out great. Just sealed it in a sanitized bucket until I got home, pitched yeast, and swapped lids for one that was drilled for a stopper with airlock.