According to a blog post on Facebook’s corporate blog, the social network company filed a lawsuit against Namecheap. The suit was filed because there were domain names registered at Namecheap under Whois privacy proxy that allegedly infringed on Facebook’s trademarks. The blog post was written by Christen Dubois, Director and Associate General Counsel, IP Litigation at Facebook.
Here’s an excerpt from the blog post outlining the lawsuit:

