As many users as Facebook, many of those users have entered their payment details, a great brand that is just as big as Facebook, and synonymous around the world with communication.
I just happen to be talking to a non-tech computer user on the weekend who told me that he and his entire family and friends overseas do not use Facebook because Skype does everything they need in terms of staying in touch and it has worked for them for years.
They should start over with the software and spin it into a web and mobile service. It is a great platform to take on Facebook with - a much simpler service for basic video or text chat, and add in some photo sharing, email, etc.
Google really missed out on an opportunity here - I bet that whatever they end up producing internally will not be merely as good or as popular as a new Skype run by Microsoft.
In terms of the price, it would almost be a worthwhile purchase with just the users and brand - the near-billion in revenue is just a bonus. Skype has near $1B in revenue, and most of the expenditure is related to writing down and amortizing assets as part of the acquisition (something that most PE groups do when they takeover a company - part of what makes some of these deals profitable and worthwhile). Number of Skype users and revenue is growing remarkably. If you look at the published financials[1], $97M was written off as cost of acquisition, another $250M was amortization of assets that were written down at acquisition. Their 'real' costs are $131M in marketing, $72M in development and $104M in administration - which brings gross profit closer to $500M+ for YE 2011. PE of 17-20 is a bargain, especially considering that Microsoft can significantly reduce expenditures by integrating the company into the web group.
I think this is a great deal, very different to ICQ (the immediate parallel that everybody is drawing) and much closer potential to the eBay PayPal deal. If done right, this could work out as well for Microsoft financially as PayPal did for eBay (remember PayPal wasn't doing so well financially at the time [2] - everybody called that deal crazy at the time as well) - add to that the potential of Microsoft taking on Facebook in the 'online communication for ordinary folk' sector - and it is a great,
[1] http://www.sec.gov/Archives/edgar/data/1498209/0001193125110...
[2] http://www.ygoodman.com/ppipo.html