Dont think he said that if you read whats there it says
sometimes we meet someone on the street or see a friend in passing
Yes , the folks that one isnt aquainted with dont get the smile or wave.
Im not saying its even possible to be entirely neutral, its easy to smile on your friends..
but by that same token the meaning of the like button has shifted from liking the photo , to- I like that person.
One could just
say they like them, or have chats with them apart from the photo thing.. and then they should know that you guys are friendly.
I like eyelight , we've been discussing some stuff and hes pretty cool guy. But if he likebuttons my pix I'd want to know why,, or at least that it was his genuine general sentiment on it.
Then I would be getting potentially useful feedback. If the button is uses otherwise, it becomes a popularity contest for personalities.