It certainly would annoy me. It's easy for me to sit here and tell you that I would remind them about the overhead and the announcements specifically say under the seat in front of you. The announcements generally even talk about being in the first row of each cabin using the overhead. The final recourse of course is a flight attendant but that's usually reserved for a more serious situation, like when I lady called the flight attendant on me for using electronic devices when they were allowed to be used. I absolutely loved it when the flight attendant told her she was wrong. In this situation, however, a flight attendant can be called and politely asked if there is room in the overhead for the bag for the person in front of you… You can almost appear to be a good guy.