I use Douban myself, so I can see where you are coming from, though I think Douban is very much an outlier in today's Chinese cyberspace, given its main demographic group comprises mainly of 20 to early 30s young adults (the so-called Wenyi Qingnian).
Douban is nowhere near as large or influential as, say, Weibo. Sensational topics discussed on Douban may spread, but their spheres of influence are restricted to the cyberspace, or remain within the confines of its demographic group, the young men and women who generally do not have a voice in a society defined by filial piety.
Popular social networking site like Weibo, on the other hand, has a very tight grasp on what can and cannot be posted on its pages. Weibo's users consists of people from all walks of life, from corporate CEOs to devote followers to the new party chairman. Unlike Douban, sensational topics posted on Weibo can sway public opinions and cause social tensions, and sometimes even press for policy changes in local governments, which is why it is being utilized by CCTV as part of its campaign against Apple in the first place.
And it's not just the government taking control of the Chinese Internet, it's that sites self-censor heavily, or else they risk of being shut down by the government without any prior notice (see the whole Yanhuang Chunqiu debacle from earlier this year). Publishing houses do the same - they are not directly forced by the government to censor stuff, but they have to do it themselves or they get shut down. (though I hear the self-censorship's been loosening up a bit - the new book written by Ezra Feivel Vogel about Deng Xiaoping's policies was recently released in mainland China and in it some passages about the Tiananmen Square incident remained intact, though still heavily-edited.)
Douban also suffers from self-censorship. Brad Pitt's Seven Years in Tibet does not have an entry on the site; Richard Gere's Red Corner used to have an entry, but it did not allow comments, and was recently removed; Lou Ye's Summer Palace also used to have an entry and got removed. (I'm just bitter that I can't add all the movies I've seen to my collection on Douban, because of the permanently-missing entries.)