Automated DMs to new followers can be a little off-putting. Because most of the ones I've received are self-promotional messages, some are even affiliate links. But I think it can be good way to say 'hello', some people don't like it though.

From what I've heard, some people schedule tweets for followers in another time-zone. I don't consider it spam at all. Twitter is opt-in anyway and scheduled tweeting is no different from 'normal' tweeting. As a user, you usually can't tell the difference.