Amazon.com Inc. plans to hire thousands of people in the area it picks as a second home from a shortlist of 20 locations. That’s worrying other companies because it could become more difficult to attract talent if the behemoth moves into their backyard.

Amazon has said it expects to create as many as 50,000 jobs paying an average of $100,000 at its new site. Supplying that many employees is a feat for any area, and is likely to result in greater competition for workers and wage increases at a time when unemployment already stands at a low 4.1% nationally, some economists say.

“We’re nervous,” says Steven Kosakow, director of talent acquisition at Lionbridge, a Boston-based company that helps firms with translation and globalization services. Lionbridge is building out its sales team, and recruiters there worry that hiring salespeople will become nearly impossible if Amazon moves in. Boston is among the cities on the shortlist.

Employers are concerned in part because there’s little known about Amazon’s hiring plans.

“No one knows who they’re moving,” says Andrew Gadomski, a consultant who helps large employers execute recruiting campaigns. Amazon’s effect on local employment would depend partly on the kinds of jobs it plans to fill, he said. Still, more competition for the same workers in general could mean that hiring decisions become protracted and firms have difficulty filling slots.