What do algo's really do?
In a nut shell they are in place to wreak havoc on momentum traders.. well no actually they are designed in theory to "add liquidity" to a thin market, while reducing the spread between bid/ask. I personally do not care if the spread is a nickel if the price is stable and not going to be whipped around by 100 shares flipped back and forth 50 times in 1 second. The wizard behind the curtain really is using these algo's to race up offers or down bids ahead of decent size resting limit orders in the book.