Something that may be useful for people who sell products or services for BTC might be something like a How-to to avoid inadvertently becoming a money transmitter. For example, does someone who sells a single Green Dot MoneyPak become a money transmitter? What if they do it a few times? What if they actually set up a business that sells items like this? How about Linden Dollars for BTC? What level of activity triggers these obligations? If your nephew visits you and you take 1 BTC from him in exchange for walking around money, does that? Pretty much anyone in the BTC community has done some kind of transaction like this.
A couple clarifications.
1) Selling goods or services (no FinCEN doesn't consider "real" currency in any form to be a "goods or services") is never a MSB regulated activity. So you can sell computer parts, gold bullion, heroin (illegal for non MSB reasons but still not MSB), diamonds, webhostings, search engine optimizations, relaxation therapy, etc for BTC without running afoul of MSB requirements.
2) It is the action of exchanging virtual currency for real currency (or other virtual currency) which requires registration as a MSB (specifically money transmitter type)*. As for "what level" per FinCEN any amount of conversion makes you a MSB if done as a "business".
Per the guidance letter.
An exchanger is a person engaged as a business in the exchange of virtual currency for real currency, funds, or other virtual currency. ... An administrator or exchanger that (1) accepts and transmits a convertible virtual currency or (2) buys or sells convertible virtual currency for any reason is a money transmitter under FinCEN's regulations, unless a limitation to or exemption from the definition applies to the person.
Looking at the actual MSB regs we see ...
(ii) Facts and circumstances; Limitations. Whether a person is a money transmitter as described in this section is a matter of facts and circumstances. The term “money transmitter” shall not include a person that only:
(A) Provides the delivery, communication, or network access services used by a money transmitter to support money transmission services;
(B) Acts as a payment processor to facilitate the purchase of, or payment of a bill for, a good or service through a clearance and settlement system by agreement with the creditor or seller;
(C) Operates a clearance and settlement system or otherwise acts as an intermediary solely between BSA regulated institutions. This includes but is not limited to the Fedwire system, electronic funds transfer networks, certain registered clearing agencies regulated by the Securities and Exchange Commission (“SEC”), and derivatives clearing organizations, or other clearinghouse arrangements established by a financial agency or institution;
(D) Physically transports currency, other monetary instruments, other commercial paper, or other value that substitutes for currency as a person primarily engaged in such business, such as an armored car, from one person to the same person at another location or to an account belonging to the same person at a financial institution, provided that the person engaged in physical transportation has no more than a custodial interest in the currency, other monetary instruments, other commercial paper, or other value at any point during the transportation;
(E) Provides prepaid access; or
(F) Accepts and transmits funds only integral to the sale of goods or the provision of services, other than money transmission services, by the person who is accepting and transmitting the funds.
and for MSB in general ...
(
Limitation. For the purposes of this section, the term “money services business” shall not include:
(i) A bank or foreign bank;
(ii) A person registered with, and functionally regulated or examined by, the SEC or the CFTC, or a foreign financial agency that engages in financial activities that, if conducted in the United States, would require the foreign financial agency to be registered with the SEC or CFTC; or
(iii) A natural person who engages in an activity identified in paragraphs (ff)(1) through (ff)(5) of this section on an infrequent basis and not for gain or profit.The part B above could be nicknamed the "BitPay" exception. BitPay is simply acting as a payment network and thus isn't (my opinion not legal counsel) subject to regulation. The part iii is likely the exemption most applicable to a user. Key words are infrequently and not for profit. Actually making a profit doesn't matter, as you could be a bad businessman as still be for profit. So if you exchange $100 into BTC for your nephew so he can get his first coin and do so without any markup well you probably are not a MSB. If you do so for 100 of his friends over the course of a year and collect a 10% markup for your time well you probably are a MSB. Ultimately the regs are very "loose" so it comes down to does FinCEN think you are a MSB (or if it gets that far does a judge agree with FinCEN determination).
Edited for clarification and included cites:
"FinCEN Virtual Currency Letter":
http://fincen.gov/statutes_regs/guidance/html/FIN-2013-G001.html"FINANCIAL CRIMES ENFORCEMENT NETWORK, DEPARTMENT OF THE TREASURY" regulations:
http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=b3dbf70d55232935bba654ea6c52ba2b&tpl=/ecfrbrowse/Title31/31cfr1010_main_02.tpl"PART 1022—RULES FOR MONEY SERVICES BUSINESSES" regulations:
http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=b3dbf70d55232935bba654ea6c52ba2b&rgn=div5&view=text&node=31:3.1.6.1.6&idno=31* Prior to FinCEN guidance the "common sense" conclusion would be that exchangers would be classified as a "Currency Dealer" but FinCEN makes it clear that this type of MSB is only for conversion between two REAL currencies. The conversion of virtual currency nonsensically falls under "money transmitter" type of MSB. So as of today an entity which exchanges virtual currency for real currency is a money transmitter and one that exchanges real currency for real currency is a currency dealer. One that does both is both. Both currency dealer and money transmitter (along with check casher, money order issuer, etc) are sub-types of the MSB.