Keeping up with an active distribution like Fedora consumes a fair amount of time, but also bandwidth. Depending on the frequency that a yum update is performed, hundreds of megabytesor even gigabytescan be required to bring the system up to date.
I went through the Fedora update archives some time back and came up with a stunning figure for the volume of updates issued over the (short) life of a Fedora release. I can't remember for sure, but I think it came out to about 12 gigabytes over the 13 month life-cycle. Almost a gigabyte a month.