I am an avid biker. You will see me along the lake around 7 a.m. most days and on Saturdays. It was busy this last week and I saw a number of bicycle accidents waiting to happen. This is the scenario - a biker comes up behind a couple of walks walking, or walking their dog, or on another bike, the bicyclist moves to the left to pass, and the dog or person moves in front of the bike.
Bicycle courtesy and safety is paramount. If you are biking or coming up behind other folks be sure to call your pass. Say "passing" or "on your left". Be sure to call your pass when you are a while back just in case in startle the person or other bicyclist and they move to the left. This happens pretty often and accidents that happen on bicycles can be pretty serious.