Facebook, Google, Microsoft...all were everybody's favorite scrappy insurgents at one point.
Once perception shifts the other way, it's hard to turn things around because everyone starts assuming the worst. This incident is a perfect example: the old ToS were standard boilerplate that appears in a bunch of other places, and had most other companies done it, it would have been seen as a non-issue. However, since Dropbox has been receiving other negative press lately (some centering around real issues, some centering around similarly trivial nonsense), that changes how every new story about them is perceived.