Maybe - check with a lawyer
You don't have to register if
You use a website (MtGox or Coinlab) to buy coins
You use coins to buy "stuff" (Namecheap, alpaca socks, etc)
You might have to register if:
- You run a wallet hosting company
The FINCen law requires people to register if they
Are a mixing service
Participate in the Bitcoin OTC market and issue one on one trades with people for cash (or cash substitute)
Run an online trading site (MtGox, or similar)
I suspect the same requirements apply for Money Orders:
- Anyone who accepts Bitcoins for any software or service (over $1,000)
However, I do understand your concern in this sentence:
By contrast, a person that creates units of convertible virtual currency and sells those units to another person for real currency or its equivalent is engaged in transmission to another location and is a money transmitter
So what does a Bitcoin miner actually do?
It performs a service for the Bitcoin network and gets paid for it in the form of transaction fees.
This value increases over time.
It is hardware that competes to solve a math problem and wins new coins for that block.
This value decreases over time.
Here is an example of a Miner that probably MUST register: A solo miner is configured to not broadcast Tx to other hosts. The miner accepts a Tx with a huge fee. This money substitute in exchange for a service is covered not by the FinCEN note in the OP's post, but implied by this link.
I think it's a grey area that isn't well described, and we should look for more guidance.
I don't like saying mining "creates units of this convertible virtual currency". I think the actual creation occurred in 2009 when the Bitcoin Protocol was launched. I would argue that the protocol "creates" the coins, and USA based miners are just claiming them.