So the tweet would be integrated into the system, as would any reporting of it. :-/
My suspicion is that by the time other people start re-tweeting this the and you can get any sort of twitter sentiment determination the market will have corrected.
Are you taking the other side of this and hypothesizing that you can determine twitter sentiment before the market reacts? If so please mail me, I write in house trading systems for a living and I'd love to chat.
(1) In this instance, I'm pretty sure I don't know how to solve the problem naively. It went onto a theoretically legit account. I would have to cross-correlate with a couple other sources of information. At any rate, it points out to me that I need to encode a 'reliability' measure of the information.
(2) Not really. I don't have the capital to operate at low-latency levels. My hypothesis is the obvious one: markets are emotional and I should be able to construct a predictor for certain industries based on emotions emitted on accounts & news snippets relating to those industries.