Fast-food workers in New York City, Chicago, St. Louis, Detroit, Milwaukee, Kansas City, Mo., and Flint, Mich., have held one-day walkouts and protests, seeking $15 an hour, more than twice the federal minimum wage of $7.25 many of them are making.
Nelson Lichtenstein, a labor historian at the University of California, said he's doubtful fast-food worker unions would be created out of the strikes, The New York Times reported Wednesday.
He said potential unions should be cautious of the current enthusiasm.
"You pour in a lot of resources, saying, 'Yes it does work,' and a year later it disintegrates," he said.
Other labor leaders said the high turnover rate of fast-food workers -- 75 percent -- makes unionization impossible.
The one-day strikes were expected to continue Thursday with a walkout planned in Milwaukee, the Times said.