Over the past 30 years--even the past 15--automation of tasks which were once done by people in the lower-to-mid tiers of the middle class. Word processors have replaced secretarial pools. Robots have replace assembly line workers. Self-service web-sites have replaced data entry clerks. "On-line" (web, e-mail,etc) have replaced tellers, postal workers, etc.
I know I'm personally responsible (due to proposing and implementing automation projects) for replacing over 1500 people since 1995. Is this a good thing or a bad? I don't know. The Industrial Revolution killed off craftsmen, but created millions of other jobs. The question is, what will the Technology Revolution leave in its wake?
So before we start pontificating on taxes, social welfare programs, and ever increasing calls for "wealth distribution"--remember to look in the mirror and ask how many people's jobs have you eliminated today?