Adage for the psychological theory that people who change to make other people happy are preferred over people who always try to make others happy.

What is most appreciated in human interaction is to change in the direction of the others.

update: Imagine that instead of a change of personality (to please someone else), we're talking about intellectual discussions. If someone says to you "I like your stuff" and another says "I don't liked it at first but then I realised how right you was!". You're going to like the one that changed its mind over the one that didn't make "any effort" to praise you...

naked_ape is interpreting the proverb differently than I do. I always understood it to mean that people can lie to you with words about their opinion of you, but if they imitate you all the time, then they probably aren't lying to please you, but think of you so highly as to want to be like you. (So one is not supposed to be angry at someone being a complete copycat of you.)

Imitation: to try and be like someone or something.
Flattery: to fawn over

If these two are compatable, a questionable theory, at best, it is a theory that says when you copy someone's clothes, hair, music, etc. you are sucking up to them and wanting to "be like Mike."

Flattery, unlike a real compliment, is motivated by a desire to gain acceptance, it is rarely sincere.

To say that imitating someone is the "best kind" of flattery is akin to saying that cursing out someone is "the least bad" kind of abuse. Not really something terrific.

(Film buffs may remember Single White Female)

This proverb is based on a theory that people who imitate you think that you are cool, so much so that they would very much like to be you, hence their imitation is an indirect form of flattery.

This proverb is usually intoned when a person complains about being copied. It is meant to soften the sting of being imitated, which is undeniably annoying. This tends to happen in a school environment; or between artists, writers, musicians, or in any circumstance when originality is held very high in importance.

I personally never thought the proverb did make much sense, as to be flattered by a person would require one to hold the flatterer in high esteem, and how can anyone esteem a copy-cat?