I've been asked a few time, and have posted this answer before. Every time I've been asked for corporate ID, the desk clerk is holding my corporate credit card in his/her hand already. Anyone can get a business card printed with anything on it, but it's much harder to get an "Insert Your Employer Here" Corporate Account Amex with my name on it. Usually, the desk clerk laughs about this, but once, a desk clerk claimed they were required to look at a business card, which I furnished without any additional conversation.

FWIW, a couple of times, when I've been meeting with a customer that has a very significant discount at a popular hotel, I'm told at the time of reservation that the customer needs to provide advance notification to the hotel that I qualify for the rate. The customers have also let me know in those circumstances (they've also told me to ask for the rate) and have a standard email a specific person at the company sends to the hotel. One of those hotels is in downtown Brooklyn, one is in Manhattan and the third is in Houston.