A listing that will close on eBay on August 20, 2010 concerns a bootleg demo of Beautiful Dirty Rich. This cannot be an authentic release because Lady Gaga never recorded with Def Jam. Note: the pre-album promo of the song is the in the GagaFrontRow collection.
A bootleg promo of Monster has been on eBay a few times now. It is not authentic as it includes various unofficial remixes made by fans.
Likewise not authorized are other promos that contain unofficial remixes, such as those by dj Dark Intensity. Some of these bootlegs are difficult to detect because they are modeled after authorized releases, though often with different tracks. (Some of the items in the GagaFrontRow collection have changed, by the way). By example, here is a bootleg remix CD of Alejandro.
Of special note is a seller by the name of cookieburch who has been offering various bootleg demos on eBay lately, such as this Money Honey disc.
Finally, as Gaga collectors will know, the Brazilian promo CDs have been an issue of debate for some time. It can be safely concluded at this point that the Brazilian CDs with unofficial remixes cannot be authentic (Examples include bootlegs sold by gagafan1974 on eBay). However, this will not necessarily apply to other releases from Brazil, nor to other releases by the merchants selling Brazilian bootlegs. GagaFrontRow will soon feature an important update on this matter, so stay tuned.
Check the Collecting Gaga page for more info.