Jack Dorsey's über-popular credit card readers got a big thumbs-up from Cupertino this week. Square's devices are hitting Apple's 235 US retail locations and Apple.com for $9.95 a pop -- plus the 2.75 percent that the startup takes off the backend each time you use the reader -- or you can always just sign up for a free one over on Square's site. The iPhone / iPad / iPod touch plug-in accepts Visa, MasterCard, Discover, and yes, even American Express. The
