Automated trading has reduced bid/ask spreads significantly (usually to the regulated minimum of one cent for popular issues). This is a compelling benefit for individual investors.

It has negatively impacted investors doing large trades, but those investors generally have more tools at their disposal to break their trades into smaller groups, or whatever. The major example impact I've heard is that the larger investors can't look at the order books at all the markets, and issue one order (to one exchange?) and take all the orders.

It seems that the automated players are duplicating their orders at multiple exchanges, and removing or replacing orders at other exchanges when one fills. A simple solution would be for the large investor to send individual orders to each exchange, and pace them so they arrive simultaneously at each exchange (instead of sending them simultaneously); of course, if you do that often enough, automated traders will probably put out smaller orders or do less duplication.