Thought I ought to cross-post something I just added to my Blocked on Weibo site:
Back in December, after I’d completed searching through half of my 700,000 word list, I decided to look more closely at what kind of words were being blocked. I used the 218 two- and three-character words that I’d uncovered at the time to be blocked only 2 one-character word are blocked: 屄, cunt / bī; and ҉, a Cyrillic character that is associated with backwards or bi-directional writing) as a sample and then proceeded to tag them according to whatever categories I began to see developing. (The categories are at the end of this post and on the second page of the spreadsheet as well.)
As would be expected, most of these three-character and under keywords were names of people (most Chinese names are made up of a one character surname and a one or two character given name). 87 of the 219 were names of people, and the vast majority of those people, 54, were CCP members. Nine of them were involved with either corruption or other controversy in which they were usually dismissed. Fifteen of the people are dissidents of various sorts. Three are criminals who were neither dissidents nor CCP politicians and are probably listed because their crimes were so gruesome.
Because of the way Weibo censors items, inoffensive words are inevitably caught in the net. For example, “grand justice” (大法官) was blocked because it contains 大法, i.e. Falun Dafa. Other inadvertent blocks included Théodore de Banville(庞维勒) because it contains 维勒, a reference to Uyghurs.
Words related to sex or sexual activity also compose a great deal of the list. This include anatomy like 女阴, slang like 吹箫 (blowjob, but literally blow flute), and “immoral” sex acts like 恋足, foot fetishes. Discrimination that would be considered wildly un-progressive in the West is also on display. Lesbian and homosexual (同性爱) are blocked, as are Islam (伊斯兰) and Muslim (穆斯林).
Finally, the list of blocked words on Weibo is actively adjusted and changed. These words were blocked at the time of their search in November and December, but most of this list has been unblocked since late-January.
Here are the categories I used to code this list:
? – I’m unsure of why it is blocked 
person – a fictional or real human with a name
place – geographical location or named geographical body
“clean” slang – slang or abbreviated phrases that are not “obscene”
sex – related to sex, sexual activity, or sexual organs
obscenity – obscene phrases
morality – words dealing with actions that might be considered “immoral”
crime – self explanatory
scandal/controversy/corruption – self explanatory
religion/”cult” – self explanatory
CCP – Chinese Communist Party
princeling – deals with children of CCP members
demonstration – related to a mass protest
dissent – related to ideas or thoughts conflicting with CCP
force / violence – related to weapons, shows of force, or violence
minority – dealing with minorities or ethnic groups in China
nonCCP politics – other political issues not related to CCP
foreign – self explanatory
internet/computer – self explanatory
other media, content, and art – self explanatory
history – either historical figures or events
inadvertant? – it is blocked because a word within it is blocked
 If other categories are checked off, it indicates my best guess.