I, too, have a ring lock on my bike (also a Breezer). I like it for use at work, where everyone drives and there is a security gate (also, I park it inside). But, I also use it for quick stops on the way home if I didn't bring my cable lock.

While I agree that someone could just carry my bike away and wouldn't be stopped, I feel we live in a safe area and the chances of that are very, very low.

Places I use it at just last week include our High School--for a track meet, library, and market. I didn't want to leave it at the market, but I shopped quickly. I would use this at our barber shop, too, and have done that several times.

When I know I'm going places like our market or Aldi's, which are on bigger roads, I take my lock.

Hmm. Is there ANY source for those ring locks in the US?
Googling, I see UK sources, and I see some cruiser style bikes in the US with ring locks installed, but no source for just the locks.

Um, where would they get the stats besides maybe video footage?

The bike was stolen - so no-one knows whether it was ridden off or put in a vehicle or just cut off like the NYC video.

Mine was just ridden off... cause it wasn't locked :o

A small lock around a chain just doesn't seem strong enough. The chain can be easily broken and the thief can just coast away with the bike using it much like a push-scooter.

If your bike has a rear disc it's really easy to put a padlock through the disc to prevent it from being ridden away. And that rear disc is not easily broken so it's a bit safer.

My old eBike had one built-in and it worked because the ebike was just too heavy to be carried away.

when motorcycle disc locks became popular after many incidents where the user forgot to remove said disc lock the lock manufacturers started including a magnet in a flourescent color to put over the ignition,

I think a much more effective combo of this type would be a lock to imobilize the rear and a MC type fork lock so you can only wheel the bike in circles, this would only be effective though if your bike weighed alot.

I wonder if you could find some thin braided clear fishing line that could stop a bike with a rider cold, attach it to the front hub, kinda like the old chain around the rear axle prank... I wonder how long you'd need it to be to be effective?

Before you accuse the OP of misunderstanding "something as simple and low-tech as chains," you'd do well to understand chains yourself. :p

If the lock is on the master link, removing the master link would indeed allow the lock to be removed. However, if the lock is on any other link, opening the master link will not allow the lock to be removed - it's still locked to a closed link of the chain. Clearly one would not choose the master link to put the lock through. Last time I checked, there were no master links that magically remove every side plate from the entire chain.

Not that I'm going to start locking my bike this way, for a variety of reasons listed by others. Too easy to cut the lock off, too easy to forget the lock and trash a chainring or a derailleur, too messy to get my hands anywhere near the chain.

If I wanted a small lock that could do this sort of freelocking I'd be inclined to put one of the miniature U-locks around the rear rim, which would prevent it from rotating past the brake caliper. As it is, if I'm going to be near the bike I lock it with a cable, and I don't leave the bike places where I won't be near it.

Well, I'm guilty of having tried to drive away with the rear disc lock still in effect. That was on my old eBike. Not a problem, I just reached down with the key, unlocked the pin and was on my way.

But a padlock on the chain could damage the gears and such so I'm a bit against that.

What if instead of putting the lock through a single link, you had a tall skinny lock that went through one link on the top part of the chain and one link on the bottom? This would solve the "lock getting into my sprocket" problem, since it would be impossible to move the chain in either direction without trying to stretch the lock. It wouldn't even need to be that tall, since you could "pinch" your chain together in the middle.

I put a bright green padlock through my rear derailer. Its large enough that its impossible to rotate the crank around it. Its intended use is as a detterent. Its a nuisance for thieves. But its not the only lock I use. A D-lock and thick cable lock are also used. I never leave my bike not locked to some thing unless its totally unavoidable. Even then, I make sure the bike is within sight and 10 metres of me.