"Blurred Lines" is a hit because it capitalizes on the retro trend in pop music, has an appealing music video, and was released on the cusp of change in the general public's music palate. Mr. THICK(E) mentioned that the song was supposed to be tongue-in-chic, so the pressed insinuating that it promotes rape culture are doing some reaching to compensate for the fact that their faves may not have a leviathan smash (my fave, fortunately, had the former longest #1 before "Blurred Lines") in the vein of "Blurred Lines".
Congrats to Mr. THICK(E), and hopefully, "Feel Good" and "Give it to You" smash. I've been on his D since "Lost Without U" (and off the Timberlake bandwagon since).
Perfect timing, loads of crossover appeal, catchiness, sex sells, its different from anything that been on pop, urban, rhythmic, AC, and HAC in the past five years.
I think it's the cross-generational appeal, similar to Adele. It's sounds very classic, while also being sort of an alternative to what was on the radio at the time it came out. Plus, the video helped give it press and views, and it's in a commercial.