Roach-motel markets: you can get in, but you can't get out. More technically, monopsonistic or oligopsolistic factor markets, where the number of employers is small and thus control hiring in the local market. (Though I would expect Nebraska to be fairly competitive in hiring, given its surprisingly large number of finance and insurance companies.)

That's another possible way to look at it, but wasn't what I meant. The companies I know that went to Nebraska (or Idaho) pretty much had everything handed to them and they're not exactly states known for being big on protection of the middle and lower class. (People in favor of the approaches taken by these states might call them "business-friendly" climates; I think being friendly towards corporations, in an age where people cheer them for being amoral, is kind of stupid.) Monopsonic/oligopsonic concerns are another one to keep in mind, though.