I noted that:
a. Free calls to landlines last max 1 minute unless you've paid a balance to them (couldn't see what the minimum balance was)
b. In the EULA, you agree to let them use your computer and bandwidth for their purposes (ie I guess you are signing up to be a relay for them)
Skype does this too I believe, but there's other companies out there who don't. Don't ask me which, Ive forgotten, sorry