Starting July next month, Twitter will be removing its 140 character limit for its Direct Messaging feature. This allows for longer private messages, making it a more viable as an instant messaging channel. In the meantime, they are making some changes to its API where developers and 3rd party clients would need to make some adjustments to accommodate to the latest changes.
This makes it easier to report problems to brand customer support on Twitter especially to airlines and telcos. With the current 140 character limit, usually one would need to split their messages into several DMs to get the full message across. Take note that this only affects DMs and the normal tweets will still retain its character limit.