That such problems as basic as incorrectly typed URLs could break Skype is beyond understanding.
I don't think it's beyond understanding. Not even a little.
Microsoft has always been pioneers of the "let's try to embed 'smarts' in stuff to make it cooler and friendlier to use" kind of thing.
Autorun on media, for instance has caused a lot of problems with things like viruses and rootkits.
Hell, Microsoft pioneered the technology which meant you could get a virus without opening the attachment of an email -- and up until then people had been saying "no, you can't get a virus simply from clicking on the email unless you run the attachment". Then Microsoft went straight to running the attachment and proved them wrong.
Microsoft tries so hard to coat the world in eye candy and do things for the user that they often go straight to the "well, you clearly want me to run that".
So in this case it probably went "ZOMG, teh URL" and jumped to running some code.
I have found over the years Microsoft's zeal to have dynamic, flashy content often means they create things which make for terrible robustness.
Like their widgets and live desktop stuff they've now had to deprecate on no less than three different platforms that I'm aware of because it was a giant security hole.
They put in a feature which says "wow, we'll just run this stuff because it's awesome", only to run smack into the wall of "but it's also dangerous".