Well spotted, the new urls are part of a change to make everything a little more Facebook (and other social media) friendly when posting links. However there should be a magic bit of code which redirects the old style to the new - it was working on our test account, but has failed to appear on live so we will get the developer to sort it asap.
Previously when you posted a link to an event it would often select one of the "facility" images to display and some text about non members being able to enter, which was less than ideal. Now you should (*) see the logo or the appropriate distance medal image plus the first part of the event desciption, which is a lot nicer and more useful.
* slight problem is that it transpires Facebook won't display an image which is less than 200x200 pixels, and guess what, the current medal images are smaller, as are most of the organisers' logos. We're working on the medals but it might take time for organiser logos to grow.