There seem to be some issues with how shift buys work in beta 9, as in some test games, my shift buy would buy 9 stocks in a player who already had 2 stocks owned by other players. Basically, my shift buy was displacing a stock owned by someone else.

That said, shift buys don't feel like they should exist under the current stock system. The dynamic of taking stocks one at a time seems important to the system because of how multiple people can participate now, and allowing people to react to aggression also seems important. Shift buys made sense when speed or price certainty were more important than the potential overpay for unowned stock, but I don't think they make much sense when the main drawback is a lower stock price in the short run.