I prefer to nag people to not use shorteners at all if you're not on Twitter. I don't know if it works, but I feel that it's a habit that needs to stop.
Shortened links are annoying and misleading, I've been wasting too much time clicking links I've seen already and links to sites I just don't like.
Also, users who actually use Twitter via SMS would probably not be capable of viewing the link anyhow so it could just say "(+lnk)" or something.
So one to one mapping to SMS is not possible now.
When I enter SMS bigger then 140 bytes it's splitted transperently and the only consequence is increased payment for that SMS.
And thus uber-shortening will probably continue until someone develops alternative processes that are ~sexier~