I agree with ChristinS.
It's not just about the 10 years but rather at what stage of life or maturity the younger person is. An 18 year old with a 28 year old is more than just 10 years in life experience when compared to a 30 year old with a 40 year old or 50 year old with a 60 year old.
Essentially the older the youngest person is the less the 10 years makes a difference. No one would approve of a 16 year old with a 26 year old and yet if the same two people got together at ages 36 and 46 it wouldn't be a big deal. However if we are strictly talking about (falling in love) with a younger person, it's absolutely possible!
The truth is most couples do not dwell on the past when it comes to conversations. We tend to talk about current events, what was on TV last night, where to go and eat, or weekend plans. This explains how people have friends of different age groups in the workplace. After a certain point an adult is an adult.