It doesn't hurt to go a little below fermentation temp, if you want your beer clean with little esters. Too low -- toward or past the lowest recommended temperature for the strain -- will just slow down the yeast, and if you're pitching yeast that was at, say, 72, you might get a bit of thermal shock too, slowing them down even more. If you're going to do this, chill your starters and pull them out of the fridge right before using them. FWIW, I do my lagers this way, chilling down to the upper 40s before pitching, then fermenting at 50-52, mainly to keep the beer as relatively ester-free as possible.
