I worked for a prominent insurance company in Ohio for almost 5 years up until last summer. I was in charge of our HR/Payroll system, Company Intranet, document imaging solution, user id management and network access control... I could go on. Bottom line, I had my hands in a lot of pies with privileged access to all. The company was becoming very strict in documenting everything, locking down permissions, etc. Prior to me turning in my notice (I knew about a month before that I would be leaving), I started working on all of my documentation, training my counterpart and making sure the company would be ready for me to leave. I thoroughly expected that when I turned in my notice, once the CIO got wind of it, he'd ask me to leave. No such luck.
They did in fact want me to stay for the two weeks and continue to train and document procedures and processes. I find it odd because I know the CIO was gunning for me to leave anyway because I was unhappy. With as much access as I had, I could have done some massive damage. But I didn't. I played the honesty card and kept my word that I'd do my best to help prepare everyone for the day when I wouldn't be around.
Bottom line, I think companies SHOULD ask an IT employee to leave when they put in a notice. I have two beliefs that back this up.
1. There should be at least some cross training going on so someone could potentially fill a role temporarily along with adequate system documentation.
2. If the employee is putting in their notice, it means they don't want to work for you anymore and could potentially hurt the company by staying. Especially if they're going to work for another company in the same industry.
Just my 2 cents
The distance between genius and insanity is measured only by success.