My first book (1987 Edition from Taiwan) taught
你在那裡做事？ 我在中國大學教書。 (Throughout the book the 口radical in 哪 was omitted.)
Ever since, I have been looking out for 做事 in my textbooks from the PRC, but haven't once noticed it. Is it just uncommon in the PRC, or does it convey a humble tone, as - I am told - 教書 does?
I think you are right - "做事" is probably only used in some areas of China, especially some southern areas where ancient Chinese has an influence, and not as commonly as "工作" in this sense. I would say it is more colloquial than the latter, too - for example, I think an interviewer will more likely to ask "你之前在哪里工作？" than "你之前在哪里做事？"
It is typically used in HK, Taiwan and rests of Mandarin speaking societies.
To streamline with planned economy policies(government assigns jobs), PRC government use 上岗, 工作岗位 to replace 做事. Since PRC adopt open market economy, 上岗 is used in conjunction with 做事， 工作， 上班. There is no special preference.
To me 做事 looks like "do business" as opposed to 工作 as in "work". 工作 sounds more like "job" to me. Just my two cents.
