I used to work for a company that offered brand-protection services. The customer would grant my old employer power of attorney to send C&D letters and file takedown lawsuits on their behalf, and we would do all the monitoring and brand-defense work, then send a report to the customer justifying the exorbitant fees.

Maintaining a trademark costs time and money. You can save money by doing the work yourself, or by using backchannels, as you mentioned. You can save time by hiring someone to do the tedious work for you. Even a single-partner specialist law firm should have boilerplate templates on hand for taking down an infringing website fast, using regular channels. I imagine that most of the cases result in no answer from the main defendant and default judgment that orders the registrar to transfer the domain to the plaintiff, who can then blackhole it or redirect to the genuine site.

A higher-service firm will also proactively scour the Internet for threats to your brand--at a higher price, of course.

I would not recommend my former employer for this, as they got bought out, and the new owner arbitrarily fired the entire development team.