Twitter limits you to express your thoughts in 140 characters or less. It actually encourages (if not teaches) you to be more creative in delivering your message by limiting the number of characters — thus, the limited number of words — in each tweet. This is in fact in congruence with the declining attention span of users/readers/followers, especially with the vast amount of information available in this digital age.
With services like Twitlonger, Deck.ly and the likes, users are allowed to override this 140-character limitation by cutting the message into 140 characters but allow the inclusion of a link that points to a page containing the full message (besides advertisements). These services are even integrated in apps like UberSocial and Tweetdeck.
In my opinion, overriding Twitter’s 140-character limit defeats its purpose. That limit is the same attribute that made Twitter so popular in the first place. I can understand the idea of shortening URLs, for they vary in size that could sometimes end up eating up the whole message before some could even be conveyed. That’s why I admire Tweetbot for they so far refused to implement Twitlonger or alternative on their iOS Twitter app.
Furthermore, Twitter users might want to consider shortening their usernames instead, so that when their names are mentioned, it won’t take up too many characters in tweets, and therefore will leave enough space for content. See more tips in choosing Twitter usernames.
How much is the probability that someone will click a link in a haphazard message/tweet? I don’t have stats to back my claim but I’m sure it’s lower than someone clicking on a link of a well constructed message that pokes the interest of the reader.