For people who do a lot of online collaboration requiring shared files or folders, Dropbox Pro accounts are definitely worth it. For $10/month or $100/year, you can get 100 GB of storage. There is also a Team account, which comes with even more storage as well as extra administrative options. It starts at $800 for five users.
For individual users who don’t do much sharing with other people, Pro accounts are less of a value. For the cost of a yearly Dropbox Pro account, one could buy several terabytes of hard disk storage. On the other hand, the convenience of *automatic syncing* between multiple computers and painlessly transferring photos from phones may be worth it for those users who have more than a few gigabytes of data to deal with. For people who are addicted to Dropbox's Camera Uploads feature (see "What is Camera Uploads"), upgrading to Pro (or transferring photos and videos from Dropbox to hard disk) may be necessary.
For more tips on how to manage storage on your Dropbox account, check out the section in Chapter 4 of Dropbox In 30 Minutes titled "Sharing folders with other Dropbox users." The guide can be downloaded to your Kindle or iPad, or purchased as a paperback. Purchasing options are listed here.