I am doing research into trends in the use of frequent flyer credits earned through business travel. If frequent traveler credits are accrued based on business travel paid by a company, should an employee retain these credits for personal use? What do most companies do with credits earned by employees on company business, for travel paid by the company? Are these credits a taxable benefit if used for personal use?

I would be interested to understand how most people accrue frequent flyer credits, and they use them.