I noticed this
[Famous MO Question](http://mathoverflow.net/help/badges/37/famous-question?userid=15019).
Its title is:
"[Difference between Principal Component Analysis(PCA) and Singular Value Decomposition(SVD)?](http://mathoverflow.net/q/64579/6094)."

It has zero votes, but is one of the most "famous" MO questions—nearly 4-yrs old.
Anyone want to conjecture how such a question became "famous"?
And whether the "famous" criteria are reasonable?