Hey, if you want to pay the same price as me, but use it as a WiFi enabled Mobile Internet Device, thats your business. I'm sure the carriers love you, free money for them.
My point was that smartphones use data, their apps use data, and that their best features use data. You may be in the vicinity of free wifi a lot, fine, use it. Security issues with that route are your concern, not mine.
Per your own words, I am not a 16 yr girl, but I can easily pull 250MBs on Twitter in a given month. I follow a lot of runners, athletes, nutritionists, and Android devs. Their tweets take up data, tweeted links, videos, pictures, etc take data. I am not using Twitter to tell the world when I'm sitting on the toilet, I'm using it to learn and improve my fitness.