Some publishers had an end of the year sale to move back-stock and generally get rid of whatever they had on hand. Fantasy Flight, Adamant, Goodman Games and several others all had big sales.
Some of them decided to kill entire product lines instead of taking the time to remove the d20 logo. Even with OBS offering to remove the logos for a fee they decided to just stop selling the products.
Casualties that I know of:
Fantasy Flight Games killed Midnight and the Legends & Lairs product lines. The eBooks are no longer available on DrivethruRPG and the new FFG website does not list them.
Goodman Games pulled many, many d20 titles (notably the Dungeon Crawl Classics line).
Adamant Entertainment pulled a number of titles as well.
So, what else got the axe?
As a counter-point, White Wolf still has the entire Scarred Lands series up for sale (without the d20 logo).