Bitcoin whales have much influence on BTC price. For example every time someone moves Mt Gox's funds, we see huge cryptocurrency sell off and price drops. Bitcoin still need mass adoption for price stabilization and volatility mitigation.
They have got this huge and drastic impact, for that we are calling them whales. They wouldnt be called as whales if theyre like other people who are waiting for others to change the prices of bitcoins. These whales are so strong that if they become joint, they can make huge turn overs of selling and buying at different rates and in different times. So better is to hope they dont let bitcoins down.