I've worked for a couple of consulting firms. At both firms, I had a corporate AMEX but the bills came to me. Neither firm had any problem with me using my Starwood AMEX (except for car rentals where the latter company had premium rental car coverage on the corporate card). It was just as easy to import personal credit card spend into the expense software as it was to import business credit card spend (both could be downloaded from AMEX to the expense software automatically, albeit poorly, so I rarely bothered).