One of the famous mantras around Web services and communication apps is that no service or application is truly complete until it offers private messaging or email. Users practically expect they need to connect one to one or one to many if they are given unique IDs, part of why you can find, outside of your traditional mail systems, ways to email one another on places like LinkedIn, Quora, Twitter, Facebook, FriendFeed and countless other networks, creating a practically endless supply of in boxes that need to be checked.
In that vein, I'd venture that there's some truth to a new extension of that phrase for 2011 and beyond - that no application is complete until you can tweet from it.
Two years ago, as Twitter's ecosystem was finding its legs, the fact that a game would offer users the option to tweet a high score was in itself news. Unsurprisingly, one of the first comments on that post was simply, "Looks like a great way to get people to stop following you..." But since that time, it seems most iPhone and Android games offer the chance to share scores via Twitter. eReaders let you tweet what page you are in for the book you are reading, and music streaming services give you the option to tweet out tracks or artist pages.
With Twitter's update to the official Mac desktop app, a contextual menu option which comes up with every right-click or Control Click is "Tweet". Tweet the words you have highlighted on the screen. Tweet the Web page you are viewing. Tweet tweet tweet. Tweet the YouTube video you just watched. Tweet the Flickr photo you viewed. Tweet the blog post you just wrote. Tweet tweet tweet.
So how much is too much? So far, it doesn't seem like there's really a limit to what is tweetable and what's not. I told the developer of a business card indexing app that he should let users tweet when their jobs start and complete, for example saying, "I just indexed 200 business cards at businessURL.net!". After all, if customers want to share your message, you should make it easier.
Now we have inanimate objects tweeting. Scales tweet your weight. Shoes tweet how far you ran or how many calories you burned at the gym. Location apps tweet everything under the sun, including who you're with and where you are. If an application exists, it can tweet. Unsurprisingly, even this post will automatically get tweeted, and you can tweet it.
Fight the 140 character limit or not, but Twitter is an ecosystem for people, services and bots. If Twitter is to be a channel of your lifestream that shares what you're doing in your life, than all the services you interact with will get a piece of your profile and your stream. If you're developing an app, before you hit publish or ship, think... does it tweet? If it doesn't tweet, maybe you're not done.