Same issue here. I don't recall seeing anything about streaming throttling in my service agreement when I "upgraded" my FiOS service from 20Mbps to 50Mbps a couple of weeks ago. However, since then my Netflix qualiity has sucked **bleep**!
Not happy and soon to be an ex-Verizon FiOS customer after nearly 10 years and THOUSANDS of dollars spent (average $130/month x 120 months = $15,600)