All of which immediately puts me in mind of Hanlon's Razor:
Never attribute to malice that which can be adequately explained by stupidity.Chances are, someone relatively new to Twitter, and presumably quite junior, figured they'd found a way to game the system, and hadn't thought through the consequences. Maybe they read one of the vile guides explaining how to game Twitter? If Habitat are criticized for anything, it should be that they (or their agency) are using people for this task who don't understand the social web. You need only look at the list of people they follow - currently 4 people - to see this was the case.
We've reached the stage now where job descriptions need to include a requirement for people to demonstrate they've participated in social networks for long enough to understand the social nuances at play. I think Habitat will recover quickly from this unfortunate incident, but we can anticipate similar transgressions elsewhere.