I started running scrum of scrums sessions a few months ago where I work, with the intention of getting the teams to collaborate and communicate effectively, particularly in relation to any areas of overlap between the teams. There are quite a few teams who work on the same project/solution, and so their effective communication is essential.
As it turns out, in most cases the communications between the teams was good, and these meetings ended up being more of a knowledge sharing session. We discussed any new ideas, tools, practices which we’ve been using, and whether they’ve worked or not. We also discuss what isn’t going so well for each team and we collectively make useful suggestions and try to help out.
So basically it’s not so much a “scrum of scrums”, but more like a “retrospective of retrospectives”