I might be an outlier, but I don't like slugs in URLs. They make URLs unnecessarily long, often forcing people to use URL shorteners -- completely defeating the purpose. They get awkward when the author changes the title. Other commenters mentioned some tricks to get around this issue, but all involve redirects. Cools URLs shouldn't change in the first place. They don't copy cleanly if you use nonalphanumeric charact…
> They don't copy cleanly if you use nonalphanumeric characters, as in nearly every language other than English. I haven't noticed this ever being an issue. At least in Firefox, non-ASCII characters will show as-is in the URL bar, but in the copied URL they will be properly encoded.
One alleged justification for slugs is that they allow people to guess what the URL is about without actually visiting it. This usually happens in forums, comments, text messages, and other places where people can only use plain text. But non-ASCII slugs look undecipherable in exactly such places.