So, with a jailbroken iPhone 4 you are able to make Face Time calls over the 3G network. Good news for fans of video calls, bad news if you've got a restricted 3G data plan.
So how much of your allowance are you likely to eat up when Face Timing?
Well 9to5mac carried out a little experiment for a 5-minute 3G Face Time call and these were the results....
Usage before call: Sent 15.3MB, Received 117MB.
Usage after call: Sent 23.0MB, Received 124MB.
So, the amount of data sent was 7.7MB and the amount received 7MB - 14.7MB in total. So that's around 2.94MB a minute, meaning a 500MB plan would let you do almost 3 hours of Face Time calling (if your terms include up and downstreams), providing you don't use your 3G data for anything else.
If you do use your data for other apps, which is highly likely, 2.94MB a second seems a bit "expensive" to us.