What I'm getting at is when does it go from investing, "I think this entity is going to take my money and use it to build a profitable factory that will then return to me a share of the profits", to just gambling "I think this stock price will change by the end of the day and I'm going to bet on it", and what are the positives and negatives of that?
The distinction between investing vs gambling and positives and negatives sounds like more the subject of a PhD thesis than an HN comment! At some point the marginal benefit of smaller price spreads from very short term trade to actually allocating physical capital and labour to producing more valuable stuff might actually be lower than the amount it simply inflates asset prices, but that is much closer to microseconds than "you're not allowed to bet against this IPO, the insiders artificially pumping its value need to be able to cash out first"...
Producers that use commodity futures to lock in a sale price need a buyer or speculator to take the other side of the transaction.