When your partner crosses over to your side, leaving one side of the court double-teamed, and the other side completely open, I think it's a no-brainer that you need to get over to the open side. Somebody who thinks, "But that's my partner's side, I shouldn't have to cover it, it's my partner's responsibility.", isn't much of a team player. It moderately annoys me when partners say "switch" because they think I'm such a noob that I'd just stand there and leave half the court open. Anyone above 2.5 shouldn't need to be told to "switch". It's just common sense, you cover where you're needed, don't be obsessed with "my side/your side" thinking. You're supposed to be a team.
I strive not to laugh at human actions, not to weep at them or to hate them, but to understand them. - Spinoza