I have heard of a UPS person being reprimanded for taking a Coke can into Pepsi headquarters.
I have heard of Citicorp rejecting expense receipts on Amex cards.
And now I hear if you are Steve Ballmer's (Microsoft) kids you dare not use Google or try an iPod. I imagine his salesfolks dare not use salesforce.com...
Update: A contractor for Intel was asked to show his personal laptop. He is convinced if it had an AMD chip he would not have been given the work
A vendor bidding for business at Delta was asked what flight he came in on night before. The Delta exec checked his reservation to make sure he had not flown on the competition.