It's not cost effective. In this case, it's looking like each arbitration proceeding will cost the employee that files it $400 in arbitration fees, and they will win at most ~$1000. Assuming $200/hour for lawyers (ha! if only), if they spend more than 3 hours dealing with it, they lose. The only reason they're going this route is because it will cost Chipotle even more: $1100 in filing fees, plus the hourly rate of the arbitrator (likely ~$1000/hour), plus their own legal fees. So it's a useful harassing tactic on the part of the class action lawyers.