If you have a big enough order, it has to be made across multiple trades. If people start seeing one buyer chasing a bunch of shares across multiple trades, th

If you have a big enough order, it has to be made across multiple trades. If people start seeing one buyer chasing a bunch of shares across multiple trades, they'll start hoarding and drive the price up. That's how a lot of these algorithms make their money, by noticing these large buys more accurately and quickly than anyone else and stepping in the middle.