If scopes in different lenses have names that are too similar to each other, results from one lens can show up incorrectly under another one. This can be most easily noticed in the home lens, but can occur under individual lenses as well.
For example, installing the Bliss lens (lp:unity-lens-bliss) and the Books lens (lp:unity-lens-books) can lead to results from the Bliss lens (applications) showing up under both Bliss's applications category and the Books category when a global search is done. A screenshot is attached to demonstrate this The screenshot contains results for the default applications lens, the Bliss lens and the Books lens, with Firefox showing up under all three. It should not show up under Books.
This happens due to the fact that the local scope in the Bliss lens dbus path is named: ''/net/launchpad/unitylensbliss/scope/main" and Books one is named "/net/launchpad/lens/books/scope/main". Using D-Feet to view dbus introspection data, it appears that the details for both net.launchpad.UnityLensBliss.Lens and net.launchpad.Lens.Books show /com/canonical/dee/model/com/canonical/Unity/Scope/main/T1321723498/Results in their introspection data. Note that 'main' appears as the final part of the scope's dbus path and the scope definition lens's introspection data.
A workaround for this is to ensure that the last part of the dbus path of a scope is unique.