Since I noticed previously you were also reading Dark Pools (commented in another thread), I found that book to pile up evidence for (b) as well. Do you have similar takeaway from Dark Pools? In particular, in the early days of electronic trading, that book clearly makes the case that the hackers (or maybe mainly Josh Levine) were completely focused on disrupting a corrupt and "good old boy" network driven trading system.

But (and I say this after having read both the Lewis book and Dark Pools), I'm not entirely sure what to think about HFT (or more broadly, electronic trading in general) and market volatility.

It kind of seems like there is going to be some popularly accepted government regulation of electronic trading that my gut tells me will be more acceptable for the "other, more brazen pickpockets" than the new, despite the fact that we think choice (b) is better for investors.