1. By means of BitMessage we can have some P2P market place. I mean "marketplace" just in terms of distributing bid and ask offers throughout anyone interested, not the actual money transactions.
2. Multisig = I can setup some kind of 'combined transaction' with the seller, where I transfer my euros to him, and he transfers his bitcoins to me, and this is effectuated as an atomic transaction (i.e. can't abort or undo half way), and this two-way transaction can only become effective after we both signed it? Or am I completely mistaken?
How does escrowing come into play here?
See here for fellow traveler's proposal: http://bitcoin.stackexchange.com/questions/517/how-can-a-single-person-operation-keep-a-collection-of-online-wallets-secure/834#834 the escrowing is used to make sure the OT server will not default on its IOU, and you want to trade on an OT server because you want untraceability(that's right, the server operator cannot figure out who are you sending money to, unlike a mixer operator). An OT server also only signs receipts, and do not store any real currency, so in case of a government raid, they will get nothing.