Most people keep them. I've seen them used for walking paths in the woods, errosion control for paths or lawn seeding, landscaping mulch, or just leave it and let it rot. Some want it just blown all over (no piles). I don't recomend it for landscape mulch, most of the stuff is 90 to 95 percent hardwood (maple, birch, cherry, and crap wood). I'm not sure who I would sell to? I've heard it can be used for livestock beding but would seem more uncomfortable than saw dust.
This customer I don't think realized how much chips there would be. Having said that, he doubled his brush piles from when I scoped out the job 3 weeks ago!