I know about unauthorized going out of bounds resulting in a technical foul, but I saw something in a scrimmage today that made me wonder.

After inbounding the ball the player ran along the baseline to the other side of the key before coming back inbounds. Call or no?

Technical foul. See casebook play 10.3.3SitB.

As long as the player doesn't step in a get the ball for an easy shot, I'd use this as a time to warn the player and explain the rule (not many players or coaches know and understand it). If he/she comes in and has a direct effect on the play, call the T. I had to call this one in a kid's tournament this year. Player A inbounds the ball, runs the length of the baseline and enters the playing court. He catches the ball wide open and hits the shot (although I was already on the whitstle waving it off when he took the shot). I explained to the coach and he understood why I had to call it.

OOB Play
 

I saw it once on a midcourt inbound. The coach had obviously called the play during the time out. The inbounding kid ran along out of bounds and stepped in by the arc, looking for the 3-ball. TWEET!