For its next trick, Facebook is proposing to displace e-mail with a unified chat-like messaging service that integrates e-mail, instant messages, text messages and Facebook messages in one "social inbox" accessible from PCs and mobile devices.

Messages from close friends will be segregated from junk and everybody else's messages.

What CEO Mark Zuckerberg left out of the unveiling the other day is that Microsoft's Office Web Apps are going to be integrated into the new and initially by-invitation-only platform, which is supposed to roll out slowly over the next few months.

Microsoft, of course, is a minority investor in Facebook and Google is a big jealous rival.

Facebook users will be able to access and share Word, Excel and PowerPoint files as attachments to their Facebook messages.

Facebook thinks e-mail is too slow and complicated. However, the new system will still start by giving users a @facebook.com e-mail address but there won't be any subject lines, cc's, or bcc's. There will be individual conversation histories, forwarding, and seamless messaging with other systems once it gets IMAP support. It integrates with Jabber but there was no talk of Exchange support, POP support or the rest of the usual corporate paraphernalia so it's more kiddie mail than anything else.

Something like four billion messages get sent everyday through Facebook.

The 15-man engineering team that's been building the thing the last 15 months - starting before Google launched Wave, another future-of-messaging vision - used HBase, an open source version of Google BigTable, built on top of the Hadoop Distributed File System, as its database infrastructure, instead of Facebook's traditional MySQL, Cassandra and Haystack.

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