Attitude and Tone Are King
With the explosion of applications and brands, I, like all humans in commercial society, have gravitated towards preferring some over others. In other news, the sky is blue and water is wet. I've found myself really enjoying using and discussing these applications with my peers, trading information about how to better use a product, or which one to switch to, even defending one over another.
Why do I like talking about them? Why should I bother giving them the free publicity and advertising? It's not always a conscious decision. Websites I do this with seem to share the following in common:
Informal language: The language used in the applications reflect the informality and anticipated use. Groupon, for example, uses informal, sometimes silly lingo, filling in what I would expect to be boring legal gobbledygook with humorous jokes and quips. This works in a positive way to support the fun environment the site is trying to create. Look, they just got another bit of free advertising because of it.
Not using formal, complex or highly technical wording lends personality—and even credibility—to the site. It feels like there are humans on the other side of the application, and they seem more honest.
Encouraging commentary: If a site or application has a lot of features, users can't be expected to read a manual. Coaching users to do the right thing, or providing simplified instructions at the tricky parts can solve the problem. Being silly or extra helpful in a playful tone is less serious, but sometimes that's ok, depending on the intended users.
After submitting a post on Google+, the service offers an encouraging "Nice post!" message, along with some tips for editing typos or changing sharing options. They could have offered the same functionality via terse links before posting, but instead offer the information like a friend sitting next to you. It also encourages uses to amend information after submission, meaning mistakes are ok. Their target audience—at least during the open preview—are technically savvy Internet users, so this sort of post-action coaching works great.
In summary: if the target audience isn't policy writers, lawyers or super-serious engineers, deliberately lending humanity—and readability—to the site's copy text in the form of informality is a great way to befriend users, and also get the point across without causing users' eyes to roll back into their skulls.