This is the (likely to grow) activity of Twitter users time-delaying tweets that reflect activity while on the road or travel, lest the axe-murderers of the world gain too much information. This is a very big deal for parents who travel frequently. Think of this as a form of "TiVO" or "DVR" for Twitter.
Example: This week I spent three days in NYC but I neglected to send any real-time tweets, a shift from my usual behavior. That said, I might "time shift" an observation today (when I'm back at home) reflecting a part of that trip experience. See example of blurb that actually took place yesterday.
Motivaton: Safety, Concern for Family, Some Paranoia
Tradeoffs: Lacks the thrill of real-time