You can view who has access to your Dropbox folders and files by opening the web app, navigating to the folder, and checking the Who has access column in the list of folders. This will show you how many members have access to the folder, along with their names. You can also remove collaborators from a shared folder by clicking the Share button and selecting Remove beside each collaborator's name. Additionally, you can view all your shared files and folders together at once by going to dropbox.com/share or clicking Shared in the Dropbox web app sidebar.