In a recent decision, the U.S. Supreme Court ruled that a prevailing defendant in a FDCPA lawsuit may collect costs from the losing plaintiff without proving that the lawsuit was brought in bad faith. Marx v. General Revenue Corp. (2013).
However, it's important to note that this applies to costs only, and not to attorney fees. In order to collect attorney fees from a losing plaintiff, the defendant must prove that the plaintiff brought the FDCPA action in bad faith or with the purpose of harassment.
To learn more and to find a link to the opinion, see Nolo's blog post: Supreme Court Says Prevailing FDCPA Defendant Can Collect Costs.