That may be market dependent because I've not seen it with the candidates I've interviewed.

I think the preception of ageism comes from the fact that more experienced employees come with with more expectations (of performance and pay). If you've been in industry ten or twenty years and havent' (by choice or by ability) then you've all but proven you're "harder" (Id say neigh impossible) to train. One of the few metrics that correlate well to performance in knowledge work appears to be ambition so it naturally results in older workers either doing very well or washing out.

The problem, as I see it, is those washouts are the ones crying "ageism" the loudest and doing their best to stifle talent entering the workforce.