I've been thinking about moving to Skinny but before I do I wanted to check through their Terms & Conditions.

Under Data Charges it says:

Skinnys data rates for included data in a Skinny Prepaid Plan is calculated based on usage and charged as follows:

• billed in 5KB blocks;
• rounded up at the end of a data session or every 15 minutes, whichever comes first, and
• a minimum charge of 20KB applies. 

(Where: 8 bits (b) = 1 Byte (B); 1024 Bytes = 1 Kilobyte (KB); 1024 KB = 1 Megabyte (MB))
So from that I conclude that, assuming I have a data session open 24x7 which every smartphone these days does, every 15 minutes EVEN IF I USE 0KB I will have a minimum charge of 20KB applied, which calculates to 1920KB in 24 hours or 13.44MB/week!!!!!

I've sent skinny an email to clarify on this because it can't be correct.