Argentina has a bit of a Socialist bent, and demonstrations and strikes are a regular and accepted part of life here. Many are announced beforehand so people can plan their day around them, others are more spontaneous, so you may find that the bus or taxi you intended to take is on strike that day.
Early this week the garbage collectors went on strike for 72 hours, so for a while Buenos Aires became Mal Aires. Last week the cab drivers all took a day off to go to the soccer staduim (and were paid by the government to do so), which I guess explains the rate increase that took affect last Sunday. And two competing rail unions have been in conflict this week, leading to some violence and a death, which then resulted in several demonstrations. On Thursday night the Government Plaza area was jammed with demonstrators but I never heard what they were demonstrating.
Here is the view at the corner on Tuesday morning.