Les Noms de Plume
The same person can post as a radical liberal on one blog and a reactionary conservative on another at the same time. One can pretend to be a pious Chassid or a depraved libertine. One could even stage cross blog petty fights and arguments between these writers when they are ultimately written by the same person.
None of this is new, although I don't think anyone has taken it as far as I imagined above. But in the spirit of uncanny coincidences of thinking and reading in my life, here is a quote from an online biography of Isaac Bashevis Singer:
Singer published his work under various pen names. Foverts featured his short stories under the name Yitskhok Bashevis, while his popular journalism appeared under the name Y. Varshavski, his political commentary under D. Segal, and his gossip and advice columns under G. Kuper.