On Dropbox, for context when a tech company IPOs there are typically "ratchets" in place that prevent all shareholders from selling stock right away, so initial investors, founders, and employees often each have their own 'hold off' time that can be anywhere from 3 months to a year.

Because of this dynamic, the stock price of the company a year after they IPO is a really interesting indicator of the 'retained' value of the company. Which is to say after anyone who has a big chunk of the company could sell (and that drives down the price) versus how many people are selling. This is where the float is maximized so the stock price is more closely tied to the market value rather than a scarcity value.

Dropbox's performance has been pretty solid in this regard, especially compared to things like GroupOn or Zynga (notable problem children) or SNAP (current poster child).

I don't own any DBX that I'm aware of (I may through an aggregated ETF so for the pedantic folks I leave that disclaimer in) but it wouldn't seem to be a "bad" investment for holding.