Yesterday was the launch of Madden NFL 11 (coverage here). Yesterday was also my first purchase through Twitter's Earlybird. Earlybird had a big offer on the new Madden NFL 11 video game - it normally retails for $59.99 but was sold through Buy.com (sans @Earlybird) for $39.99.
Considering the savings and the timing - it was a compelling offer... and it sold out after three offer releases over a two hour period.
Interestingly, the promotion did not lead to a significant increase in Twitter followers for Buy.com (@buy_com). Despite the offers buzz, Buy.com only gained ~300 Twitter followers. Ultimately, I imagine that they are valuing the promotion in part to increased social buzz / presence (as I imagine most purchasers were like me: in and out with only a discounted video game).