From Priceline.com:

There are two ways to purchase airline tickets with priceline. You can purchase a ticket at a listed price and select the airline and flight times that best meets your needs, or you can Name Your Own Price ® and save even more on your airline tickets. Rules and restrictions will vary depending upon how you purchase your ticket.

Earning Miles:

If you purchase your reservation from our list of available fares and flight times, you should be able to earn frequent flier miles for your flight, but there is no guarantee. Because frequent flyer programs vary by airline and are subject to change, we recommend that you verify eligibility by contacting the airline directly. Please be sure to enter your frequent traveler information on our website when purchasing your reservation. If you did not enter your frequent traveler information at the time of purchase, you can ask an airline agent to do so when you check-in for your flight.

If you have purchased a Name Your Own Price ® ticket, then you will NOT earn frequent flier miles for these flights. The Name Your Own Price ® tickets provided by our airline partners already include deep discounts and therefore are not eligible for airline miles.