Dear Rich Staff periodically finds infringing copies of its eBooks posted at websites or blogs. Instead of writing to the individual user, we send a DMCA notice to the company that owns the blogging service or the web provider that hosts the site (the Internet Service Provider or ISP). The ISP (assuming they're not in Rumania, China, or some other country where the locals don't fear U.S. copyright lawyers) typically removes whatever is complained about -- for example, an infringing picture at a blog, an infringing movie at YouTube, etc. By promptly removing the material, the ISP is given a "safe harbor" meaning that the ISP can't be sued for infringement. The ISP then may write to the individual user who maintains the blog, website, or YouTube account and inform them about the Notice to explain why the music, movie or eBook is now missing. The individual user then has the right to file a counter-notice. (We explain the procedural aspects here.)
What's an ISP? We believe that if the copyright owner sent the notice to your friend's coffee shop, then your friend's coffee shop is beng considered as an ISP. An Internet Service Provider (ISP) also sometimes referred to as an Online Service Provider (OSP) is any business that provides access to the Internet. That includes big access providers like AOL, Yahoo! and Google, or it can refer to companies that provide website hosting, commercial wi-fi services, or file-transferring (FTP) services.
What's confusing about your friend's notice ... A DMCA takedown notice is intended to direct the recipient to take something down from the Internet (or disable access). This is obviously something within the ISP's control. We're not clear how that would work in the case of a wifi coffee shop. If there are standalone computers at the coffee house, perhaps the notice is requesting deletion of bit-torrent files -- for example, if the in-shop computers are serving as bit-torrent clients. But if the customers bring their own computers to the coffee shop, we're not sure what can be "taken down." More information is needed. (BTW, if this answer seems disjointed, it's because we stopped mid-answer to make ourselves a cup of coffee. We've fallen pretty hard for the Blue Bottle party line and we can't seem to free ourselves).