There is a large amount of linguistics literature about what sentence-final
ne and
yo actually mean, and the question is not totally settled.
The basic analysis is that by using
ne, the speaker implies that the information given in the sentence is already known to the hearer, hence the usual "canned" translations of "right?" or "isn't it?", which may or may not make sense in a particular situation (because translation is an art, not a science). Generally, the purpose of "stating the obvious" with
ne is to ask for confirmation, or just for small talk. If the implication is not true (that is, if the hearer was in fact not aware of that information), it may be rude since the hearer can get the embarrassing impression that he doesn't know something he is supposed to know.
Yo is the opposite: it implies that the speaker is giving new information to the hearer, that the hearer didn't prevously know. Again, it may be offensive to the hearer if he was in fact already aware of that information ("Is this guy taing me for a fool?"). By the way,
yo ne, which is also common, is like
yo but softer and less assertive.
This analysis works fine most of the time, but it fails to explain some special cases. See the very good recent book of Hasegawa for more information about this (and many other things) and some pointers to the literature if you are interested.
http://hasegawa.berkeley.edu/Cambridge/introduction.php
