Conventional wisdom has long had it that short DNS TTLs are bad because they increase query loads and any faults in DNS will cause availability problems more quickly.
It seems popular now though for large sites (e.g. twitter.com, github.com, ycombinator.com, stackoverflow.com just to name a few) to use relatively short DNS TTLs, between 1 and 5 minutes, presumably to make failover easier.
Has popular opinion around short TTLs being "OK" changed? Are these sites doing something special to make this viable?