I don't think it's quite accurate to call Twitter ephemeral, though. All kinds of third-party services are trying to index and archive as many tweets as possibl

I don't think it's quite accurate to call Twitter ephemeral, though. All kinds of third-party services are trying to index and archive as many tweets as possible, plus there's always the possibility that Twitter will cut a more formal deal with Google (or any other search engine). Plus, there have been numerous documented instances where deleted tweets can still be found by Twitter's own search engine. In short, the old rule of thumb still applies: if you don't want it archived and indexed and preserved forever, don't put it online in the first place.