I've written a blog post some time ago that doesn't directly refer to Tulpas, but does somewhat answer this question of the social desires that I fulfill through this method. I think this sufficiently answers your question, although if you feel like it doesn't, let me know, and I'll write something for Tulpas directly.

http://tuxedage.wordpress.com/2013/04/22/the-least-accepted-part-of-me-a-defense-of-waifus/