Some of them are Clanless because something went wrong during the Embrace process, and they did not get enough of their Sire's essence passed along to them to imprint them with the abilities and weaknesses of their parent clan. Others are embraced by a Sire who has Diablerized several members of other clans recently and thus passed on essences of several clans with none predominating. Still others once had a clan, but have diablerized enough members of other clans to have diluted their own blood essence to the point that they have more foreign blood than their own coursing through their dead veins.
Since Gehenna, most Caitiff are at least nominally friendly towards the Camarilla, for protection from Crusader Teams and the Sabbat. However, in the 1950's one Caitiff known as Joseph Pander led a faction of Caitiff to join the Sabbat against the Camarilla, and thus Caitiff in the Sabbat are known as Panders in his honor. Pander himself was confirmed killed during Gehenna, but many of his followers still are among the Sabbat's membership today.