Internet Sharing legal?

[Table83]

Pretty much everyone that comes onto this form uses some form of teathering for their phone, PAAM, and what not. It's not that hard to do.

Sprint charges tons for these services though. Currently I am in a spot that leaves me completly reliant on my Internet Sharing for my internet usage. My questions are

Can I get into trouble for doing this?

Will sprint be able to find out that I'm using it on my computer?

Can they legally do anything (can't I do what I want with my phone internet)?

I've heard through the grape vine of Sprint charging for teathering if you pass up some limit on your data plan, but has that actually happened to anyone first hand?

Any other advice would be greatly appreciated because I couldn't find any good forums on this anywhere on the net.

Thanks!