I'll cover money laundering first since it seems to get so often repeated here:
No, exchanging bitcoin for cash, or vice versa, is not in and of itself money laundering. Replace "bitcoin" with "casino chips". Is every casino in Vegas behind bars? No. Why not? Because there was no intent to launder, only an intent to exchange value for value.
Secondly, the concern over bitcoin dealing being a Money Services Business (MSB) is a little more legitimate. IIRC, FinCEN has already stated that these sorts of businesses are MSBs, and require all the usual compliance measures attached to that label. There are also some states that consider bitcoin trading businesses MSBs as well, on the state level. On a practical level though, hardly anyone is enforcing these rules. Does that mean there's no risk? No, of course not; there's definitely a risk. It's just not currently that large of a risk.
Lastly, with regards to unreported income, that's an issue with any income, regardless of source. If a stranger handed you $10 out of nowhere, that's income and you're required to report it. Hell, if you sold some crack to that stranger in exchange for those $10, you're required to report it. Unreported income is not a bitcoin specific concern.