Yes, text uses less bandwidth than vox, but web access uses even more. Unless you can just text directly to facebook.
I'll be frank- I don't text. I tried to find a phone plan that doesn't even have the capability. I don't use facebook, which I consider the land of kids and pervs and makes youtube look like a classy place. So maybe there is a leap of logic here that I'm missing.
But I still think that the kids should be spanked, and the parents put in the stocks.
I text quite often, actually. There are plenty of times when I want to update someone on my whereabouts, eta, change in plans, etc., and I don't want to place a call and leave a voicemail message should they not answer... I know that they will get the text (almost always) and can review it more discreetly than calling voicemail. You can also send but one text to many different recipients, which is very difficult to do with voicemail, if not impossible on most plans.
Plus, ask yourself this question: aren't there times when you want to send a message to someone but would rather not actually talk to them over the phone, or negotiate with their voicemail?

Texting is also much cheaper than using your minutes. I get something like 250 texts/month for $5, and pay for the minimum monthly plan of 500 shared minutes.
I also refuse to text while driving, unlike some crazy people I see on the road these days.