Its International Workers' Day, and Baidu Is Banning Forums on "Workers," "Strikes," and "Proletariat"

Baidu's 2013 May 1 Doodle shows people
building a wall.

According to Baidu's "Encyclopedia" (百科 “Baike” a wikipedia service) entry for "May 1" (五一):

On July 14, 1889, at a meeting of representatives of various Marxist and Socialist countries was convened in Paris, France. At this meeting, the French representatives proposed: designate May 1, 1886, the day that American workers struggled for an eight hour work day, International Proletariat Day.
１８８９年７月１４日，由各国马克思主义者召集的社会主义者代表大会，在法国巴黎隆重开幕。这次大会上，法国代表拉文提议：把１８８６年５月１日美国工人争取八小时工作制的斗争日，定为国际无产阶级的共同节日。

These screenshots, taken on May 1, 2013, show that Baidu bans users from establishing forums on its PostBar (Tieba 贴吧) service on the following topics: Marx (马克思), Socialism (社会主义), Proletariat (无产阶级), Workers (工人), Labor Unions (工会), and Strikes (罢工).