@kat I disagree. In a messaging service I expect to be able to reply, forward, add additional recipients to the conversation, &c. This can't be done if those recipients are on different systems, rather, it can be done if recipients are on different systems by explicitly cutting'n'pasting replies and recipient lists -- which is especially awkward on touchscreen mobile devices for which these systems are designed. Not having one standard client for ALL my contacts creates a HUGE cost. Which may be why I'm on so few messaging systems. /cc @theru