Probably always. Just three nights ago a very good friend said to me, "You'll flirt with anyone, anytime."
I think he may be right.
But, in my defense, flirting need not be a bad thing always - - when I do start up a conversation with a guy I find attractive, I usually am asking/commenting on things I truly want to know/etc. Omg -- I sound pathetic.
Ha!
I'd probably start up a conversation with the guy in your question image -- right after that darn woman gets out of the way! :) Nah - - he looks too interested in whatever she's saying. :)