+1
If I did that, my intentions were to check warranty and see if it is a legit ipad. Other than that, I can't think of anything else they can do with the serial number.
... Unless if the person is a serious hacker.. knows how to look up your iTunes account with the serial number linked to it.. probably using some sort of exploit and fraudulently charge your iTunes account on a whole bunch of stuff.
Is it possible? I can only presume so. Is that the persons intentions.. who knows.