How does review sites gets so much content written?

[rudla25]

I just wonder how the large review sites gets so much content written within such a short period of time? Okay large sites may hire a lot of people but how about the mediocre sites. I see many of them gets updated twice or thrice or may be more in just one day.

Its not something that they may have planned in a month or so. Say the product is launched yesterday and they are producing reviews within just a couple opf hours.