Does putting your mac to sleep damages harddrives?

this might be a silly question, I was told recently (by a mac technician) that putting your mac to sleep can damage hardrives, is it true?

I put my mac to sleep almost very night cause its too loud to leave it up all night and i hate switching it off and booting the following day

No, they are completely wrong. Macs are designed to sleep rather than be shut down. No worries

i was a bit sceptic about it but i just wanted to make sure as i just bought two new drives

Apple wouldn't knowingly implement a feature that could potentially damage the machine.

I just put the display to sleep, ive gota quiet imac tho and i sleep with a fan on.

OS 9 has a bug in the energy saver setup that can cause a crash on waking. Eventually the crashes can cause software problems (preference corruption etc) but it does not cause hardware failure. Also, there was a firmware update for early G4s on OS 9 (http://docs.info.apple.com/article.html?artnum=120230) related to hard drive longevity.
No version of OS X has ever had either problem.

You will be fine putting your computer to sleep. In fact, I'd advise that over shutting it down. It takes about 2/3 seconds to start back up when it's asleep.

This feature has been around for at least 5yrs in both PCs and Macs - drive makers design this in (fast sleep - fast wake up) -- and to me it all about saving power anyway --- the HD in my old HP did this fine for 3yrs and was going strong