Not sure it would be legal, but I would put a significant amount of devs onto predicting stocks. A blog goes more silent or people start Googling for "what is fraud, exactly?" from IPs known to contain lots of IBM workers (that would be more on the illegal end for sure). Obviously a lawyer would need to review every input, but they have access to machine learning and data so much so that they could rock the exchanges…
I recall Eric Schmidt saying they thought about this, but the lawyers told them it would be illegal so they didn't explore it further.
Seems like so much untapped potential.