For my opinion, the one who abuse "FUP" are the telco themselves.
"Unlimited" with "FUP"? Why don't just call it as "QUOTA", since it is a fixed amount.

For my opinion, FUP is fair usage policy, which mean when server detect your abnormal activity, such as bypassing torrent thru VPN, or when the tower overloaded, so the traffic sharping is kick in so everyone in the network have a fair speed eg: average 1mbps for every one, or server detect someone using some illegal equipment such as booster which will not fair to the others, then FUP only kick in to control the users.

Malaysian telco the one abuse the FUP term as quota only.
Unlimted with quota.

Only fixed lined in Malaysia do not enforce "FUP".