My parents gave me a text-capable phone when I was 14 and starting high school, it was actually right when texting was taking off, I was the one dragging all my friends in to it!
As far as I know, they never checked the messages, if they did, they never told me. However, I suspect they didn't because I know what kind of trouble I was getting in to! Knowing what I did manage to sneak past them, they probably should have checked

. That said, I only got myself in to serious trouble once, I wrote some things I shouldn't have on a livejournal (remember those?) and it got me in trouble at school. They were none too pleased about that, but they handled it pretty well, didn't fly off the handle. I learned a valuable lesson. It is in fact
still out there today, though it's old news now. Let that be a lesson to you (and your kids), over a decade old and I can still find it pretty easily. I'm pretty lucky that I didn't get in to more trouble!
Overall, I think I came out pretty well, I have a solid Disney-funding career, a degree in two different fields of engineering, a retirement fund and an excellent relationship with my friends and family. My point is not that being unchecked didn't bite me, my point is that I was a good kid, and (I like to think) pretty smart and level headed, and I still managed to get in to some awful trouble because I thought I was too clever not to. I am really, really lucky nothing worse happened to derail my life. So I support parents checking on their kids until the kids are 18 and need to be solely responsible for their actions.
Also, don't take away that my parents didn't pay attention, they did, texting was just beyond their level of understanding at the time, it wasn't well known yet. They paid very close attention to everything else, always knew where I was, who I was with, and they were reasonable but firm when I tested my bounds. I think that's a major contributing factor to my success, and I appreciate it, even though I found it annoying at the time!
Fun story, I was once at a gaming convention at a local college campus when I was 16, I had some older friends that dormed there and invited my whole group of friends to stay the night. My parents reluctantly agreed, and when I saw things were starting to go sideways I texted my mother I wasn't comfortable and she made it a point to call me and demand I come home, so I could tell my friends that I had to go because my mom was just so unreasonable, and save some face. Having mommy stomp down was actually less embarrassing than admitting I didn't want to hang out there, she took the heat for it just so I didn't have to!
Matt