MileagePlus Shopping is offering 500 UA miles for every $250 in spend, up to 2,500 miles now through 12/31/12 11:59 PM EST. Shipping and taxes are not eligible for the bonus and you’ll have to wait 8-10 weeks for the bonus miles to post to your account. They are also currently offering double miles at several of their online retailers.
[...] eShopping mall has sort of matched United’s offer of 500 miles for every $250 in spend, though AA sets the limit at only 2,000 miles, whereas UA caps it at $2500. Check out the AA offer [...]