My point is having sex with people you don't know is stupid. (No sarcasm). You shouldn't need to ask for ID because the person shouldn't be a stranger (and 14 year olds may look 20, but they certainly don't sound 20 and even if they are 16 and you are no longer at school, really, have some self respect).
Sex with people you don't know implies that either:
A) you couldn't care less about them as an individual and are just looking for a hole (or indeed dick)
And/or
B) you are unable to find somebody willing to have sex if you are in a well lit room and you are both sober and they have met you before.
To be fair, I can imagine that many teenagers find themselves in situation A or B. If you are not a teenager and you are still finding yourself in either situation, really you have a problem.