I don' t have a list of urls right now, but papers on the lack of anonymity of bitcoin and bitmessage are not hard to find. It is a very difficult problem against NSA level attackers. Masking when content is being exchanged by exchanging something on a fixed schedule seems like one of the few things that can be done to at least mask something.

Edit: OTOH, this this does just mean they attack one or both nodes if they care when content is being sent.