Website efficiency is a red herring. If you've got volume problems, you can upgrade the iron, or you can turn off the volume. If they're trying to do the latter, the least efficient way to do so is killing the tickets issued: the volume doesn't drop immediately, ill-will is generated, and you'll have costly collateral damage. Screenscrapers don't have an infinite number of IPs, and blocking IPs, limiting the number of daily attempts, or just increasing the delay between requests will all work better than cancelling a bunch of tickets.
On the other hand, if I were running a carrier that saw a sudden spike in fuel prices, and wanted to shake the lowest-paying customers that were suddenly unprofitable, I might be tempted to pull such a trick.