Have had the same from someone I knew who wanted critique and feedback on his CV. Got a nice lengthy email with the CV to start with. After going through and providing the feedback I didn't hear a thing for months (until the next version for an updated attempt was sent)! Even a one-liner 'thanks' would have been better than nothing...
What is it with 'kids' these days? Didn't their mother teach them that manners helps the world go round...?!