So there is this debate about the impact of flying mounts on the epicness of WoW experience, sense of danger that the outside world should have and the PvP factor for many realms.
Since we cannot just delete them (that should be wasting lots of work and a useful resource), why not then just make fly to have a cost? Yeah:
If you want to fly you will have to pay gold for each second. Want to fly with faster mounts? You will pay more.
That would make flying mounts to be there just to be used as a last resorts for many and create incentives to use ground mounts more often. That is how it happens in RL actually, you just cannot keep flying forever.
Of course there are very rich players around that would keep flying like if nothing happened, but come on, they have earned it somehow.
What do you think?
Edit:
We have a penalization for resurrecting at the graveyard now, with gold. And we have a penalization for resurrecting several times, with a time delay. Maybe a likewise formule could work?