switched wire

I've taken down some shelves with lighting that were connected to a switch. The left hand switch used to light up all three shelves at once. The other switches are for other lights in the room. I was wondering if there is any danger in just disconnecting the switch and pushing the wires into...

I am trying to wire back two ceilings lights in adjacent rooms but on trying to identify the "switch wire" in one of them I find 2 of the 3 black wires are live! How is this possible? Two should be neutral and one, the switch wire, live. In the other room it's OK, one live out of three. Help please.