Dropbox is a service. The installer creates a set of directories where data is stored locally. Everyone who joins the same Dropbox account has local copies, and Dropbox takes responsibility for keeping everyone in-sync.
I only suggested it as a possibility, just to force you to think outside the box a little. There are many ways to skin this cat of sharing files. And what makes sense depends on the purposes for which you need to share these files, the equipment you have available, skill level, security concerns, etc. Dropbox is just one example of another approach, one that can make sharing files a lot easier. In the early days of the 'net, most ppl probably did use FTP. But a lot has changed since then, and now many different solutions exist that are more efficient, more secure, and relieve you of the burden of managing your own solution.
Let me give you an example of what can *possibly* go wrong. Suppose one of your users is on the road and using the free wifi at a local café. As a convenience, most free wifi is UNSECURED, meaning all transactions (unless protected by SSL) are “in the clear”. He decides to access your FTP server and as luck would have it, some hacker is sitting nearby sniffing the open traffic (believe me, it’s a trivial exercise). Boom, in an instant he has the FTP login. A smart user would have used a VPN to secure the connection before attempting the FTP connection, but since you can’t control your users, you’re at their mercy. But had you used a solution like Dropbox, none of this would have been an issue since Dropbox has already taken care of this issue for you – it uses SSL secured communications.
IOW, it’s all well and good to “roll your own” solution, but it also places a heavy burden on you to know all the issues, all the things that *might* go wrong and compromise not just your FTP server, but maybe the rest of your network. I’m not saying you can’t or shouldn’t do it yourself, only to be *careful*, esp. if your experience level is limited. That’s why *sometimes* it’s better to leave the solution in the hands of someone who has already considered all the issues/threats.
We haven’t even considered other issues, like ISP and free wifi providers blocking ports. FTP is a more complex protocol that it might at first appear. It can sometimes be difficult to navigate through firewalls w/ this protocol. You might want to study the issue of active vs. passive FTP to see what I mean.
But in the end, do whatever you want. If you want to setup an FTP server, create accounts, manage those accounts, manage the firewall, take responsibility for securing that information and backups (if applicable), etc., then go for it!