Yes...algo trading is legal and it is not always sinister.Some...

Yes...algo trading is legal and it is not always sinister.

Some investors use them to simply sell a large parcel of shares or vice versa. It is available to everyone (if you have the stock to warrant it) you just have to cut a deal with your broker.

Don't get too caught up with the manipulation theories as more often than not it amounts to nothing although off course if there was a takeover in the pipeline then they would usually employ a bot to aid in their purpose.