Tread carefully out there. That well-intentioned hashtag you just crafted: it’s branded without being cloying, it’s set to engage, you’ve gone and prepped some very cool assets — you are waiting with bated breath for it to go viral. Who doesn’t love cats after all?

But oh! What’s that you see in your stream? You’ve just stoked the ire of the Internet. Moreover, they aren’t exactly trolls but customers with real complaints. Your hashtag has been hijacked.

While in hindsight is very easy to see why the New York Police Department’s #myNYPD attempt was an exercise in futility, it might not have been so obvious for the U.S. Postal Service last month. On the whole, their Twitter campaign looked pretty benign. They even brought in Spiderman for a photo op.