You're certainly correct that it doesn't look like a true Priceline auction structure. My use of a question mark in the topic name was more tongue-in-cheek.

Nevertheless there may be some valid logic to United's venture. As other forums have commented Priceline is a hit and miss proposition, with most of their tickets coming from a couple of airlines (Delta, TWA, and soon-Continental). If United posts a decent selection of deeply discounted (albeit highly restricted) fares they can capture travelers who dislike the uncertainty of the auction concept. If United also allows mileage accumulation, they in addition capture their loyal clientele (please UAL, don't make an error on this point).

This type of concept is also a continuation of UAL's slow methodical attempt to minimize the travel agent distribution network, and its perceived high expense factor.

But then again, I've been wrong before ...