Here's a video of leg lock specialist Ikuhisa Minowa finishing off Gilber Ivel with the toe hold. This fight took place a few years back at Pride Bushido 6.
Check out this MMA video where Gregory "Blade" Babene and IIlay Malyukov both go for a leg lock at the same time. Usually when two fighters go for a leg lock at the same time, the fighter with the better technique wins. Babene finishes off Malyukov with the toe hold submission.
If don't believe how dangerous the toe hold leg lock submission is, check out this video of Ninja Girl (Megumi Fujii) finishing off her opponent using the toe hold.
If you're a fighter, and you want enhance your submission game with the toe hold leg lock submission, check out this nice instructional video put out by the Gracie Academy
Here's a video of how to get the toe hold submission from half guard
The toe hold is so dangerous, that some amateur MMA events, or submission grappling events don't allow them. This grappling event did allow them. Check out the video to see how this grappling match ends.
If you're a fighter, even if you don't plan on adding the toe hold submission to your arsenal of attacks, it's still a good idea to watch the videos and be aware of it, so you can defend the submission.