[natrius]

If Twitter doesn't check for a valid response at each URL, then this will be possible anyway. If it does check, then this wouldn't be possible anyway.

[solutionyogi]

Twitter gets millions of tweets and I am sure good percentage of them will have URLs. And if they start checking valid response for each URL, I think soon they will have to build a new data center just for this task. Also, what if the URL is temporarily down? What should they do?

[natrius]

I don't think they need to check for valid URLs. My point is just that disguising text as a URL will be possible regardless unless you check for 404s or ellipsize the URLs. Using a URL shortener isn't necessary to make URLs count for a constant character length.

[alanh]

Not true at all. Sites can be configured to respond to arbitrary subdomains.

[natrius]

Hm. I thought of that case before I wrote my comment, so I'm not sure how I wrote something that didn't take that into consideration...