[mdorazio]

Think you nailed it here. For example, in the consulting world you can pretty easily calculate the dollar value of employees at different levels based on the rates you can charge for them, the hours they bill, the new revenue they bring, and their compensation. That calculation tends to put a pretty hard limit on salaries for people not willing/able to make the transition to highly billable SME or partner-type business development/practice management.

In more traditional corporate roles, the compensation path is tied pretty heavily to growth in managerial skills and subject matter expertise in ways that don't always have parallels with software development. Even there, though, I've started seeing similar "ageism" as the article points out come into effect. Clients I've worked at have started coming to the realization that younger and more tech-savvy workers can often get to, say, 75% of the value of a 20-year employee for half the price in compensation.