a.) The domain polimedia.us (which hosts MPEx) gets confiscated by a government authority?
In case the domain is confiscated or otherwise lost MPEx would move to a different domain, in a different jurisdiction. Should the same happen again, MPEx would move to what will at the time be a solid alternative for a free Internet, be it the TOR netword, namecoin or some equivalent based DNS or any comparable solution. No government will ever be able to stop the Internet, in general. We're prepared to show this in the particular.
This is by the way true of all the other polimedia properties, which probably should be given a few words. Romania is a small market. As such, the same person happens to own the most widely read blog in Romanian (
Trilema), the Romanian digg/reddit (
fain), the Romanian 4chan (
dtng). Such concentration may be rare in other language spaces and inconceivable in English, but it is a fact in Romania due to the smaller size and relative backwardness of that language space. The owner has elected to list them all under the same domain. Other people might have made different choices.
b.) The sytems that MPEx is hosted on are confiscated by a government authority or breached by a criminal?
Should the systems be confiscated or otherwise lost the service will failover to different systems, possibly on bulletproof hosting if need be. This to the point of availability.
Internet-facing machines do hold copies of the database. They are reasonably secured, which probably means they are more secure than most any other bitcoin-based application at this time. However, their absolute security is not considered a strategic priority and no extraordinary measures are undertaken to ensure it. Provided that an attacker manages to breach one or all such machines it would be possible for that attacker to acquire a copy of the list of all accounts (not emails, but keyids), their transaction history, assets and so forth. If you follow Step 1 above even in this scenario the attacker gains no benefit : he now knows that "someone" owns so-and-so assets, which is information he could have compiled anyway watching the tickers on irc/twitter etc. If you do not follow Step 1 above it is possible for your assets holdings to be identified in this (unlikely) scenario. If you value your anonimity do follow Step 1 above.
From
the FAQ, as to compromise.
In the unlikely case that the continuation of MPEx becomes impossible, all issuers will be provided with lists of their assets' owners. A successor system would have to be constructed, but no information is lost (since people can still sign with their keys, it is trivial to identify yourself as an owner).
