Express frustration towards people who use coffee shops as a free workspace without purchasing anything, and describe an angry encounter with one such person.
I hate the WiFi hoboes who take up a chair at Starbuck's and never buy a beverage at all. 
I even had a chair that I had claimed by placing my shopping on it while I got my coffee taken by a WiFi hobo sk*nk. She sat there for 30 minutes with her device plugged in and never bought a thing. 
I regret that I didn't accidently spill my coffee on her. Next time.