Although you can do it, converting points to cash is costly. A $100 Gift Card burns 35,000 points. At the Renaissance New York Hotel 57, the 35,000 points can redeem a 1 bedroom suite equivalent to $429. Redeeming a night delivers better value and can be done by ordering an e-certificate in the name of the recipient.
One of my co-workers does something like this... what he does (we all travel extensively) is he redeems his points for the Marriott Gift Cards, and then uses those for his next stay at a Marriott property. Then, when he expenses the hotel, he gets the cash back for the amount spent on the hotel. He averages about $3500 a year cash back this way.
I do agree with the others, though, when they say that you get more out of the points by redeeming them for rooms and the like.