I'm not really clear on what is being reported to the IRS. What information, exactly, is Coinbase handing over? Just names and email addresses? A list of names and associated bank account info? A list of all transactions in chronological order?

For example, when I signed up for Coinbase, I think the only information that I gave them was my email address and real name (and not my social security # or other tax ID). I did give them my bank account info, though, which is where I think the real issues could come from. For example, if someone reports $20,000 in income for a year and the IRS can clearly see that hundreds of thousands of $$$ have been flowing through a bank account, then there might be a red flag.

Definitely an area worth keeping track of, to be sure.