I worked for a company a few years back and we had a project to add a feature to our product (a dashboard for small businesses to manage their listings on Yelp,

I worked for a company a few years back and we had a project to add a feature to our product (a dashboard for small businesses to manage their listings on Yelp, Citysearch, Foursquare, etc). The new feature would let them create a promotion like 10% off, post it to their listing pages, and let customers redeem using a QR code. We planned out all the epics (create promotion flow, promotion landing page, redeem flow, etc) and sprints. I think it was six 2 week sprints, or about 3 months. Then the scope creep happened. We agreed on just a "send now" button in the designs, but marketing decided that a scheduling feature was necessary. Somehow we got bogged down building the scheduler and doing timezone calculations (e.g. what if a business located in Pacific time has an owner in Eastern Time who is traveling to Central time, when should a promotion scheduled for 6pm actually get posted?). In the end we ended up taking twice the estimated time for a feature that was only used by 0.2% of paying customers (it turns out that businesses either already have a coupon system or they don't want one at all).