Add info on federated MRs

ideas.md

@@ -77,3 +77,11 @@ individually with no clear connection.
 - **Relevant Issue:** https://gitlab.com/gitlab-org/gitlab-ce/issues/4013
 - **Mentor:** Pending
 - **Skills:** Rails
+
+Federation is very important; one of the biggest problems with the modern
+Internet is that the web has become totally centralized.
+
+This proposal fits with Git's distributed nature, since it would allow
+collaboration across different GitLab servers or even to other services such as
+GitHub. You could e.g. fork a repository hosted on a company GitLab server to
+GitLab.com and still do merge requests.