For fun I where checking some word count usage in books written in China with Googles Ngram. You can easily detect major events in Chinese history from that: E.g. The usage of 我 sharply increased at the dawn of the Republic of China, dropped significantly when Mao grabbed power and once again during his great leap forward.

http://books.google.com/ngrams/graph?content=我&year_start=1800&year_end=2008&corpus=23&smoothing=3&share=

The word 同志 (comrade) is probably even more fun:

http://books.google.com/ngrams/graph?content=同志&year_start=1800&year_end=2008&corpus=23&smoothing=3&share=

Some words such as 天安门 still puzzles me. Why the spike between 1972 and 1979?

http://books.google.com/ngrams/graph?content=天安门&year_start=1800&year_end=2008&corpus=23&smoothing=3&share=

The selection of books is maybe not 100% accurate when it comes to exact word frequency in daily usage but for those sort of indicators they are fun.

interesting stuff... google has everything these days!

The statistics for 同志 might have actually spiked a bit if we could extend the range out to today. It's become a somewhat common word that can also carry with it the meaning 同性恋. Though I'm not sure if that usage of it has made its way into books yet or not.

The use of 同志 to mean LGBT's is mainly limited to HK, TW, Singapore and Malaysia. In the mainland, it's better to avoid using this word in this way. Please remember that the number one there is called 习近平同志.

@pts, Even still it's openly listed on 百科 as that being one of the possible translations. Tier 1 mainland city folk would be more likely to use or recognize it though.