Enlarge When we looked Google's Project Fi's cellular service at launch, we worked out that the pay-per-MB service was great for people who use a small amount of data or needed a flexible amount of data from month to month. It didn't make sense for people who consistently used a ton of data, though, as you could essentially rack up an unlimited bill. Now Project Fi is trying throwing a bone to big data users with "bill protection," a cap on the amount Project Fi will charge.