The answer is "YES" (the number of users of both has increased about 60% in the last year), but why did I ask the question?
I recently join a couple of LinkedIn Groups ( Steel Manufacturers and Processors - 6000 members - took some time to be approved, and Steel Professionals - 3500 members). Groups put you in contact with people who have similar interests and I was interested in promoting a client ( Tomsin Steel - Click Here to Like their Facebook Page ).
From one of the Groups, I was able to get 25 new LinkedIn Connections - well worth the effort if LinkedIn lasts - Thus the question above.
Internet Marketing requires you integrate your use of Facebook, LinkedIn, and Twitter. We also use Ratepoint for effective email marketing and control.