We get that question pretty often, so let us try to clear that out.
Here are a couple of things you should know:
LOCKED MODE (Default mode):
1. When you collaborate with other users on a specific workspace, by default, everyone will be able to see all tasks posted by the members of this team (members who got invited and joined the workspace). Note that except the creator, the assignee and the administrator of your workspace, no one else can EDIT them. They can only view them, and post comments on them. They can’t change a deadline, edit labels or change the person in charge for example.
2. If you want more open collaboration, and let everyone from your team interact with all of your workspaces’ tasks, we recently launched a new setting for that, it’s called an “unlocked” workspace. Once that feature activated, anyone from your team can : complete a task, edit labels, set deadlines and reminders, change the assignee, etc. Anyone can do anything! Your workspace is not public, just editable by all the members of that workspace.
PS: TASK LEVEL PRIVACY:
On Producteev, you can also select who’s seeing each and every one of your tasks if you want to. Click on the ‘privacy’ feature in your task detail panel. If you want to hide that “get my boss a birthday present” task in your team’s workspace, you can do it :)
Those settings are only available from the web app for now, but obviously reflect on all of the other apps once approved.
Hope that helps!
UPDATED ON MAY 7, 2012: Thanks to @stoweboyd for helping find the right terminology for “Locked’ and “Unlocked”!