As an occasional bicycle rider married to a bicycle commuter, I have another point for walkers on the likes of the B&A Trail, the Northern Central Trail, etc.:

Groups walking together--families, friends, etc.--have a propensity (it truly must be innate in humans) to end up walking side by side in packs that can spread all the way across the paved section of the trail.

Human roadblock.

I can't count how many times I've been forced to ride off into the grass beside the trails (in violation of the trail rules) to get around a pack of humans walking side by side across the whole trail.

As much as I might agree that on trails bicyclists are like cars and the pedestrains are like cyclists on the road and cyclists on trails have a duty to slow down and wait for a safe opportunity to pass pedestrains. But still pedestrains should have the duty to either hear and heed the warning given by cyclists (no headphones) or look behind them before "changing lanes" or making a u-turn.

This is essentially what's expected of cyclists on the road and should be expected of pedestrians on the trail.

And please if you are a pedestrian wearing headphones and make a u-turn into a cyclist and they manage to miss you by inches, say "thank you" as that is about as good as it can get under those circumstances.

Just make sure you put as much emphasis on the word "passing" as on "left". Otherwise, I for one am apt to move left, as I think I have been requested to.

Mr. Schwarzwalder, you don't need to be impressed that my dog will stand by my side. Please DO understand that I am 99.9% absolutely certain that you won't seem "wrong" - frequently for atmospheric/environmental/something somewhere smells funny reasons - as you pass us. By standing still as you do so, I am ensuring that we won't find out what that .01% margin of error might entail. Really. We'll move aside, but don't YOU slip into pretension and try to determine whether or not we should be moving.

Amazing. Bicyclists insist that cars follow them for miles at 10 mph or less because they refuse to stop and let cars pass safely but they demand pedestrians get the h*ll out of their way on a trail so they can continue to ride at full speed. I say you can't have it both ways. I wait for you in a car on the road, you can wait for me on a trail.

Mark
I've ridden bikes for decades. I've been passed by thousands and thousands of cars. I'd say the longest a car has ever been forced to follow is for 1/4 mile. And that's been less than 10 cars ever. And that's because I was a part of a large group.
If you are following bikes for a mile or more than it's your problem.

A good start, but Monte's list needs some refinement and rebuttal:

1. Agreed. I’ve heard this abbreviated to a simple “left” and never known any non-hermits who didn’t know what it meant. Same with escalators and roadways, the slower party belongs on the right with passers to the left. This is not breaking news, Cheap Jim.
2. I’ve never in all of my walks/hikes come across signage saying that stepping off trail is prohibited. Would you rather my doggie doodle in the middle of the pavement? (I definitely have to stop for that.) There are plenty of reasons why a walker might temporarily leave the main trail. No reason to be uptight about it. If you are, then we'll be uptight about the posted speed limit for bikes, which is almost always ignored.
3. There’s no reason walkers can’t enjoy the entire trail when the entire trail is available. Just like empty parking lots get used for driving practice. It’s not your call or anyone else’s to determine how a trail is enjoyed off-peak. That said, if we mis-judge when “peak” is, and you round a bend only to find hikers who are “all over the trail,” then a simple jingle of your bell 50 meters out will kindly remind us that we're not alone in using the trail.
4. I’m not stopping with my dog to impress you. (Seriously, this is what you thought?) It just so happens that if my dog catches sight of wildlife or another dog on the other side of the trail at the exact moment you go past, then we’d all get a very unfortunate lesson in dog vs leash vs bike physics. Stopping is best for me and teaches my dog that he’s not to move or cross in front of moving vehicles. We enforce this lesson on all our walks, no matter where we are. Around bikes, cars, strollers, etc., we stop; we yield; we are deferential. Dogs can get into too much trouble if we don't. (I've digressed . . . .)
5. Agreed. Though if you see ear buds and the trail allows you to take a wider pass, that, too, could spread goodwill. No need to do an intentional “buzz.” No one likes a vindictive cyclist.

And in response to Alexander:
Groups cycling together--families, friends, etc.--have a propensity (it truly must be innate in humans) to end up riding side by side in packs that can spread all the way across the paved section of the road.

Bicycle roadblock.

I can't count how many times I've been forced to ride on the other side of the line (in violation of the road rules) to get around a pack of humans biking side by side across the whole road.

In general, just asking that we all follow the rules of the road or trail.

The rules of the parks usually instruct hikers to stay on the trail. The people who walk off the trail are not always dog owners and they tend to go off the trail on either side, making their actions unpredictable. And they are apt to sprain ankles etc. because the trails are meant to be walked on, not the sides of trails.

Please stay to the right and when a bike is approaching keep moving and stay predictable like you would if you were driving.

Of course state passing on the left.

Micheal:
What goes for cars goes for bikes, 'Cars (and bikes) hard, people squishy'. Bicyclists need to avoid hitting people at all costs.