You know about Amazon's Kindle, right?
https://www.mobileread.com/forums/showthread.php?t=7606
Maybe Borders feel they need to have a foot in the eBook market too. Perhaps so that people come to associate them with eBooks before Amazon completely dominates the market.
It's also possible Borders get a cut from CONNECT sales. The margin on electronic books must be huge (they can be basically produced by exporting the electronic manuscript file, very low production costs). So for every Reader Borders sells for Sony, they get a % of, say, 10 online book sales, which is what an average Reader buyer may purchase.
Just an idea.