Experienced authors tend to chastise vanity press victims for not doing sufficient research, but the murky web of vanity partnerships - and the uncritical coverage which invariably accompanies same - makes it difficult for newer writers to chart a safe path.
Some vanity presses are very good at crafting a veneer of legitimacy, one which can be very convincing to those starting out. Infamous vanity press conglomerate Author Solutions figured this out very early on, creating partnerships with Penguin, Harlequin, Writer's Digest, Random House, HarperCollins/Thomas Nelson, Hay House, Reader's Digest, Lulu, and Barnes & Noble.