It's pretty clear that the correct way to link to a phone number from HTML is with a URI like tel:2065551212. However many browsers also accept telephone URIs with slashes, a la tel://2065551212 even though this is AFAICT not allowed by the relevant RFC (3966).
So, my question is this: why do some people recommend using slashes? Is it just a bad habit from http URIs?
Or... Were there actually some early mobile browsers that did not properly recognize tel: links without the slashes? I have read at least one blogger indicating that this is the case, which is a poor but understand excuse for doing so. Can anybody provide an example where tel://### would work but tel:### would not?