http://mpex.co/?mpsic=S.MPOE
2.1. Neither Mircea Popescu, MPOE or MPEx nor their respective Owners, Directors, Agents or Partners assume any liability for any losses suffered or alleged to have been suffered by any third party as a result of the execution of this Agreement. All third parties are to make their own determinations, satisfy their own due dilligence policies and assume for themselves any and all risks involved. In particular compliance with any laws, rules or regulations in effect in any jurisdiction where a third party may find itself is entirely the responsibility of that third party -- neither party to this Agreement makes any guarantees or representation as to the legal status of this Agreement in any third party's jurisdiction.
2.2. BUYER BEWARE. MPOE/MPEx shall be considered a high-risk speculative investment. Past performance of the site is no guarantee of future performance. Past profitability is no guarantee of future profitability. Value of S.MPOE shares may rise or fall over time and the entire venture may become worthless for any number of reasons. Neither Mircea Popescu nor any other person or entity shall be liable or responsible for compensating any shareholder for any value lost by a depreciation in the value of shares of MPOE/MPEx.
2.3 At no point shall the obligations Mircea Popescu arising from the execution of this contract exceed the value of his interest in MPOE/MPEx. The liability of any person or entity party to this contract, either direct, indirect, incidental, tortious, punitive, exemplary or otherwise shall in no case exceed such sums as may be proven that person or entity has in fact received through the working of this contract. Signatories and investors agree to indemnify and hold harmless any party from any claims that may exceed such sums.
While there I found this bit interesting :
4.1. DISCUSSION OF CONFLICT OF INTEREST. The named individual is in fact at the time of this agreement the sole proprietor and operator of both named corporations, and they were represented in this agreement by him. Consequently the dispositions of this agreement may be regarded as declaratory rather than contractual in their substance. Nevertheless, inasmuch as they are publicly made and verifiable their execution or breach can in fact be verified.
4.2. This contract is the sole and complete agreement between the parties and to the subject matter. This contract supersedes and replaces any other agreements, communicated in any other way at any point in time. This contract stands as it is, and may not be modified by third parties, irrespective if said parties should style themselves "court of law", "judge" or otherwise.
4.3. This contract is protected as copyrighted material. It may not be reused by different parties without the express permission of MPEx.
So is this contract (and "this contract" is used many times) is really a declaration ? I take from this that effectively if you involve yourself then you agree to the declaration and the obligations for MPOE/MPEX/MP are not contractually binding.
As for the wider SEC issue I expect that they might be looking to track BTC from the US. At a guess they might be looking for BTC linked to the Silk Road or any other of the busts/scams that have gone down. Also if they are increasingly treating BTC as money (a wider good thing) then BTC "leaving" the US might (in their view) be subject to the reporting regulations etc.
Finally I think they were doing their job in asking.... sending an email to ask costs nothing and you never know what people will do if you just ask nicely. They might give you more than you wanted or asked for. I'm not saying that's *right* though, legally or morally.
Of course now they need to go through channels so unless they prepared in advance then it'll be a week or few while lawyers are consulted.