[xz9]

A username or password could contain ":" which would cause many checker programs to skip that line.
In addition to this, url's will often contain ":".

.TSV is the superior format as tabulators are virtually never used in url's, usernames or password fields.

[Shuu]

This sounds more of an issue with checker programs? Do most checkers even support TSV?

[Cataleya]

I see @tail always complain about it XD