fc2.com is really massive in Japan, it shows up in my (japanese language) google search with a very high frequency. And since it's Alexa data we're talking about here, it probably makes a difference that IE usage is still relatively high in Japan.

fc2, from the times I've come across it, feels like it's somewhere between blogspot and tumblr in size. I don't know how big pinterest is compared to those two, but fc2 feels big.