Is it possible for a man to receive his smicha simply from the fact that the Jews of his time all agree he should be a Rabbi? (I know this leaves out the ceremony part of it.) If a man so clearly has the learning, knowledge and ability to be a Rabbi, is it possible for him to become a Rabbi simply on that merit, if everyone around sees it? This question was spawned from the question about Rabbi Moshe Feinstein's Smicha.
Rambam (San. 4:11) allows for recognizing actual halachic semicha (with the ability to give fines and punishments) with the consensus of "all of the sages of the land of Israel". This is, of course, even if they did not have semicha, otherwise even 1 can give it.
I would call this a theoretical issue, as getting all those Jews to agree not very practical (just google Rabbi Yaakov Beirav), especially since the Rambam himself was hesitant to give give such a psak.
Other than that, I'm with msh210. You can call him a Rabbi, but what he can do with it is based on custom. Plenty without semicha teach Torah. I'm pretty sure that those without semicha will only hold an unofficial position in a synagogue, but still perform the duties required of a Rabbi. And, like nsh said, he can't give semicha.