What is the problem with high-speed trading in your opinion? I see a lot of people wanting a Financial Transactoons Tax, but I have yet to see étaples of what it would accomplish or prevent?
http://www.economist.com/node/21525456 for the starter.
The arguments in favour of speculation, in general, rest on assumption of intelligent trading and diversity of strategies. The short term range, however, is entirely up to software tools, whose decisions are stupid and have identical systematic errors. I think the short term trading is going to go out with a bang first time there's any interesting software-level exploitation - either a direct hack or adoption of one bot whose decision theory makes non-trivial use of understanding of other instances of...
The last point reminded me of speculation from the recent LessWrong article Conspiracy Theories as Agency Fictions:
Before thinking about these points and debating them I strongly recommend you read the full article.