It all depends. Sometimes you want the faster caps, sometimes you don't need to cap fast.

People who double up on mid at the start - that annoys me. But if we are trying to take the windmill - by all means please double up and lets cap this tower faster.

Yep, I admit I've leeched point caps from time to time for stupid amount of points your get. Even if a cap is 80% done, clicking in for that last 20% gets you the full 40 points. Doesn't help the team, but if your score is low it keeps the raging idiots from scapegoating you. Score is broken Riot, fix it or remove it.

the more people capping a point the faster it caps. Your gimping your team if your both caping and you fall off to defend, its better to help cap because the enemy champ thats coming to stop you now has to either blow 2 cd's to get you both to stop (unless your standing beside each other and its an aoe) or 1 cd and auto attack or 2 auto attacks. either way you had a better chance of nutrilizing or taking a point with 2 people channeling then 1 person channeling and another defending from enemy champions. Unless that 1 defender has ungodly amounts of cc (leona anyone?)

There are plenty of times it's best to just sit and cap the point with a few people. It's not black and white. I still see a lot of people only help cap in an attempt to get points though