Well, for one thing, one should keep in mind there was also a lot of legit stuff stored on their servers, along with the copyright infringing stuff. And this legit stuff was the baby thrown out with the bathwater.

Ok, I'm not defending the whole enterprise or what he did. According to most sources, they knew exactly what they were doing and they deliberately encouraged users to upload pirated stuff with various incentives. Still, according to a study, the closedown had one interesting effect. Box office revenues were hurt! Say what you say about the findings, but I find it hard to dispute them when take into account the following:
1) Megaupload wasn't the only such service by far
2) it was, however, one of the largest individual such services
3) this is a reputable university we are talking about, and not a paid research organization
It made up a great chunk of pirate traffic on the internet and as such it really does have an effect. The takedown was the equivalent of piratebay being taken offline.

Oh, and what do we generally hear from MPAA/RIAA et al. about the effects of piracy on box office? Huh? Anyone? :P
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Yes. I can haz a biz and site, no?