Relationships are built in person, except for getting "married" on EverQuest when you're 15.
> I give my students my phone number and encourage texting.
That's a disaster waiting to happen.
> …sending Facebook messages…
I hope to God you've got separate profiles for your personal life and your professorial identity. And being connected to their personal profiles? Another disaster waiting to happen.
> I get to expand the classroom well beyond our 2.5 hours per week and create a sort of 24/7 learning environment.
Mostly what you've done is destroyed any ability for you to have a life and do your own research. Reminds me of the jibe that people used to give to Linux enthusiasts, "Linux is only free if your time is worthless." You've abrogated any expectation that your students respect your time—you're on-call 24/7.