Skype on a cell phone.
Early reviews of the Skype initial public offering documents can basically be summed up as, "Boy, it's got a lot of users. I wish more of them paid."
Skype is, of course, making a little bit of money, but even so, "the Skype IPO has the makings of one of those hot deals - one that has a dash of irrationality attached to it," says GigaOm.
Over at TechCrunch, Erik Schonfeld points out that only 6 per cent of users pay.
That's either a huge growth opportunity, or a reflection of the fact that few people are going to ever pay.
TheNextWeb focuses on Skype's sensitivity to the charges it must pay carriers for Skype calls to numbers on their systems, and how any changes in those deals could vaporize a lot of the company's earnings from its main cash-generating product - paid calls from Skype to phone numbers.
Follow Streetwise on Twitter.