Yesterday Borders Group management announced that the bookseller is up for sale. A "difficult economic environment" has spurred executives to consider strategic alternatives, they said.We find it interesting considering that the company had a pretty good quarter, at least compared to how some retailers are faring lately. Same-store sales at Borders stores rose 2.1% year over year during the fourth quarter, while even Waldenbooks, its quickly vanishing mall chain reported a 1.2% increase. Profits were only slightly down from a year ago, at $84.7 million compared to $87.7 million. Plus, the chain is even rolling out a new prototype.So who is going to buy this owner of 509 superstores? Pershing Square Capital Management, its website-less investor that is providing the retailer with $42.5 million? Barnes & Noble, which, according to reports might consider a such a deal? Private-equity investors, who we haven't seen much of in the retail industry so far this year? Could it be a player north of us?Or will the economic conditions that are spurring management to sell dissuade most buyers in the end?