Dan Gillmor takes a pretty sceptical view of Facebook’s new messaging system.

In a feature that Facebook thinks is great — and will thrill law enforcement and divorce lawyers — every conversation will be captured for posterity, unless users delete specific messages or entire conversations. Do you assume that the people with whom you communicate are saving every text message and IM? You’d better.

That’s only one of the things that makes me cautious about the service. Facebook’s privacy record is spotty enough already; trusting the company to archive and protect my communications? Not so likely.

Om Malik is much more complimentary:

Facebook has not only reinvented the idea of the inbox, but it has gone one better: it has done so by moving away from the traditional idea of email. One of the reasons why Yahoo and Google Mail have struggled to become entirely social is because it is hard to graft a social hierarchy on top of tools of communication. If you look at Gmail – it has most of the elements that are available in the new social inbox, but they are all discrete elements and give the appearance of many different silos, being cobbled together.

Facebook did the exact opposite – it imagined email only as a subset of what is in reality communication. SMS, Chat, Facebook messages, status updates and email is how Zuckerberg sees the world. With the address book under its control, Facebook is now looking to become the “interaction hub” of our post-broadband, always-on lives. Having trained nearly 350 million people to use its stream-based, simple inbox, Facebook has reinvented the “communication” experience.

The deadpan NYT report on the new initiative is here.