I took a quick look at XStreetSL for old time's sake, and sure enough a LL ad shows up quite often each time I reload or navigate around the marketplace. Before the listing taxes announcement, I would rarely, if ever, see a LL banner ad on XStreetSL.
I'll let the commenter who blew the whistle on the XStreeSL ads sum it up for me:
I would suggest this is a combination of desperation at trying to get some fresh ads up there and the beginning of their push to make xsl work friendly - which is never will be.Until the Lab comes clean and kills the listing taxes in favor of a more balanced solution, expect things to only get worse for the Commerce team.