I'm certainly not a Skype expert, but I have used it in the past and it's pretty cool.

It definitely seems like there are some advantages to using it, not the least of which is encryption of the voice stream.  

Regardless of whether it is truly hobby worthy or not, with half a billion user accounts out there, I'm wondering why it has such little adoption in the hobby (or so it seems).

how? Skype is blocked by all the mobile providers.  Unless you don't mind finding a wifi connection everywhere you go.

Yeah, I would do something like use a laptop or tablet, and then use a Wi-Fi connection with it.

On top of the Wi-Fi, I would run a Web Proxy or some sort of anonymization service.  On top of that, I would use Skype.  In theory.  Not sure if it would work.

I only carry a cellphone with me.

In addition to the fact that it has been blocked by most wireless internet service providers, I also tend to believe that most providers tend to be discreet and don't want to show their hand too much. After all it is all most pulling teeth with them to show themselves on their websites with the blockage of some parts of their anatomy.

I have never used Skype but I thought that Verizon was putting a Skype application on their Android OS phones.  Does Verizon block incoming calls even though they promote this service?