DISH Network (DISH) shares are getting clobbered today after rival DirecTV (DTV) late Friday announced that it has cut a deal with AT&T (T) to sell a co-branded version of the DirecTV service starting after Jan. 31. AT&T previously had a distribution deal with DISH.

Deutsche Bank’s Doug Mitchelson this morning responded to the news by cutting his rating on DISH to Hold from Buy; he chopped his target price on the stock to $31 from $51. He writes that the loss of AT&T “calls into question DISH’s ability to grow subs in 2009.” He says that AT&T will contribute 441,000 gross adds to DISH in 2008, and about 213,000 net adds–or more than the total 150,000 he expects for DISH as a whole.

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