The companies also entered an exlusive marketing arrangement that will have Concur promoting Amex corporate cards, and Amex global commercial card business exclusively promoting the Concur expense management system.

Although their marketing deals are exclusive, Concur and Amex said their systems will continue to interoperate with other expense management systems. Half of Concur's users already use Amex cards.

At last check, Concur stock was up $6.11 at $42.16. (Update: CNQR closed up $5.15, or 14.3 percent, at $41.20, a new 52 week high.)

I wonder if investors are hoping that American Express buys the rest, or they're just anticipating the deal will boost its business.

Amex is also getting a seat on the Concur board -- taken by Amex Vice Chairman Ed Gilligan -- and the option of buying an additional 1.28 million shares during the next two years at $39.27.

From Concur CEO Steve Singh's comment in the release:

"Our partnership with American Express expands our market presence and broadens our distribution capacity. This is tremendous validation of Concur's industry-leading on-demand services, and we look forward to working with American Express to help our clients drive even more cost out of their businesses."

I always thought Oracle or Microsoft would snap up Concur. Could this make the company even more attractive to them?