get their own SL number and receive voice calls from real-world phones
Technically, of course, SL has phone service already - Vodafone set up shop in the virtual world a year ago, and in October this year launched the beta version of InsideOut, a service that lets avatars call and text each other on virtual mobiles, as well as other Vodafone subscribers in real life (provided they live in Germany, where the service was launched).
But it's also pretty pricey - Engadget says that a voice call will set you back 300 Linden dollars a minute, while an SMS costs L$300 a pop. Based on the latest exchange rates, that works out to about $1.13 per minute or per SMS. Ouch.
But hey, that's life under a telecoms monopoly. (Remember those‾) There's even an arbitrage option from YouNeverCall, but that's for internal calls only, not dialing out to real-world phones.
On the bright side, Vodafone doesn't have an exclusive 15-year license, so there's plenty of room for competition, even if they aren't exactly queuing up to get in (apart from setting up branding exercise/play areas like Telstra's "The Pond" and BT's "Area 21", I mean).
And honestly, there haven't been too many compelling reasons yet to get them to bother. As a Web 2.0 social experiment, SL is a fascinating work in progress and has plenty to teach us, but as a business environment, it's still got a lot to prove.