[theBobMcCormick]

I can send a letter or a package to my grandma via USPS without her having to pay any subscription to USPS or "sign up" for USPS in any way.

Now, the early days of the telephone system might have been a better comparison to use in your argument than USPS. But I think it could be easily argued that the early telephone offered something much more unique for it's time than Facebook does.