When consultants, partners, sales people, anyone really, send me a invitation to a Skype call, or a Google Hangout thingy, I always ask that they call me on my office phone. If that's not okay, then we'll just have to make due with email.
I'm not going to look for my headset, figure out how to use the right inputs and output, or sign up for a Google account because someone wants to call me. I have function telephone with a good wireless headset that just works.
I do the same, but international phone calls are still rather impractical compared to Hangout / Skype-like tool of choice. And this is coming from a Linux user who doesn't get supported by many such tools :) At least most tools have a way to dial into them from a standard phone.
I use it the most, but that is not comparable. I am just saying that, because I had X situations where somebody told me "Add me on skype", and then i say look, no.
