People so far have mentioned B&N as a source of reference for the Bookaccino's gag, but you know what I think the joke may also be about? Starbucks. Have you ever tried to use a Starbucks gift certificate? I can't tell you the number of places that prominently display "STARBUCKS COFFEE" as their store name but DO NOT ACCEPT Starbucks gift certificates!
Every time I've encountered this, I've heard a variation of: "Sorry, but we're affiliated with Starbucks but not really Starbucks." It's crazy -- they have their logo splattered all over their walls, they wear the uniform, use their cups, but they will not accept those gift certificates. It's a scam!