My single worst interview experience was an on-site five hour marathon of whiteboard coding, with a grumpy senior insisting that the code on the whiteboard be syntactically correct. Nothing screams "we want unthinking ticket crunching machines" like optimizing for candidates willing to focus on writing code by hand for hours on end.

Naturally, I rejected the follow-up interview, but I fear that more companies now are going to demand this nonsense.

Side note: in my personal example, the whiteboard session wasn't the reason I turned them down; I asked every person on the team roughly how many hours a week they worked and not one of them answered the question (instead redirected the conversation towards "you can work from home sometimes!" type answers).

Since then, however, I have rejected other companies trying to ape this style flat out. A short half hour, fine. Five hours? Pound sand, I say.