@David: I can definitely appreciate your concerns regarding one-minute granularity feeling too long to deal with unexpected events. Two things to consider:
(1) There are many large and very successful quant funds managing $20 billion+ who rebalance daily, weekly, or monthly and have no automated ability to react to sudden market events intraday. Not at sub-minute frequency, not at minute frequency, not even at hourly frequency. That may sound crazy, but it's probably not as big of a liability as you might suspect. Again, I'm talking about automated reaction; obviously in case of armageddon, fund managers can always manually intervene, just as you would be presumably be able to do at any point with a live Quantopian strategy, with or without the one-minute granularity restriction.
(2) Your concern is related to sudden, unexpected, violent market events. It's tempting to think about these events like real-life emergency situations where the alarm bell rings and alerts you that you have 20 seconds to get to safety before the reactor blows. In this kind of situation, you clearly don't want to be asleep for the next 60 seconds. But in a sharp single-stock or market-wide price change, it's less obvious what to do next. As an example, your strategy suddenly wakes up on an alert event that a position you're long has dropped 10% in the last 6 seconds. What next? Liquidate? Suspend trading that name? Increase your position? Hunker down and see what happens next? Designing automated safeguards into your strategy to quickly and automatically react to extreme events is actually pretty difficult to do; backtesting it on sparse event data is even more difficult.
I'm not trying to be a curmudgeon here: you have every right in the world to say that you want the ability to code automated reactions to extreme events in real-time. I'm just trying to point out that if you lacked such a capability, you'd be in very good company among professional quant and algo traders. For a typical lower-frequency strategy, I really wouldn't consider waking up every minute to be "flying blind" or taking a crazy risk.
There is a whole separate discussion topic on how to build appropriate safeguards into algo trading platforms. Typical safety features would often include a combination of "big red buttons" that allow human beings monitoring algos to suspend trading / cancel trading when bad things happen, and low-level controls that prevent algorithms from going off the rails: limits on shares/orders/dollars/messages per second, capital limits, risk limits, limits on the number of open orders/positions, etc. These are the types of safeguards that you'd be crazy to omit.