That's a common belief that I never bought into.
Your walking around all day, so your calfs are getting thousands of light weight reps all the time. They're used to this, so why train them with more light weight reps?
I say hit them heavy with low reps - something they're not used to.
Or sitting calf raises. That's a angle they never get hit with during daily activity.
My 2cc's.
BTW my calves aren't good, so my results don't prove the effectiveness of my theory. http://i10.tinypic.com/524hbub.jpg
for calves I'll do ten plates using leg press usually for 55 fro 2-3 sets sometimes after I'll do a couple sets 33 reps but not always and on a slow when I'm feelin pretty gassed I may just go 33 for a few sets. don't usually get that good burn until about halfway through and then the last 1/3 or 1/4 is the best part!!!