After a lot of work went into this survey, I can proudly announce here that it is finally accessible for you:
Senaratne, H., Mobasheri, A., Ali, A. L., Capineri, C., Haklay, M.: A Review of Volunteered Geographic Information Quality Assessment Methods. International Journal of Geographical Information Science, 2016. (Preprint available here)
Please also find some thoughts on this in Muki’s blog.