Using a Droid as a Tethered Modem

i use it and have been using it, i had it on my blackberry never saw a charge for it, cause verizon has no real idea bout how your using your phone, for all they know you could be spending all day on youtube watchin videos

...while having Slacker or Pandora running in the background the whole time and shopping online and downloading ebooks. Some of these streaming programs use a lot of data. I just downloaded tons of NES roms right to my phone. I've also downloaded lots of apps and backgrounds and pictures. Those aren't huge files but I am using a lot of data. I wonder what system they will put in place if any to protect their interests regarding tethering. And what amount of data usage will flag you?