Why is just an ID in the URL path a bad idea for SEO?

Question

Why is it a bad idea to have a ID in the URL in terms of SEO? How does this URL http://example.com/user/1234 hurt SEO?

Can someone give me a practical e

Answer 1

It's always a bad idea to provide unusual information. Try the user name instead!

For SEO there is no real advantage/disadvantage between static ID urls and username urls.