I prefer to let users retweet via prepared status update, not by making them authorize me to be allowed to tweet on their behalf. However, the prepares statuses only work if the user is already logged in to Twitter. Otherwise the prepared message will be lost when the user has logged in.
Therefore it would be interesting to know if a user is logged in to Twitter, so that I could forward him to another page telling him to log in first if necessary. Perhaps there is a hacky way to get that information? What are your experiences, are prepared status messages ok, or does twittering on behalf of the user work better in general? Björn