The big market moves of Wednesday and today are a great illustration of how deceptively easy the market appears along with the potential for stellar gains and/or losses.

The chart above is  ES market activity for Tuesday, Wednesday, and Thursday of this week. I included Tuesday to show you a typical trading range for the market - about 15 - 17 points in a day. The market moves on Wednesday and Today were more than double that with a 40+ point range - giant moves!!
Viewing the completed chart makes it look fairly orderly and straight forward- market drifts, then dives sharply, then recovers. You might even be tempted to think the movement looks pretty predictable and easy to forecast. Ah, but things aren't as easy as they appear. Cover up the 3/4 of the right side of the chart, and slowly move the paper to the right, and try to predict where the market is headed. Not as easy or predictable now, is it? =) That's what traders face trading real-time - trying to gauge where the market is headed with only past data/charts as a reference/guide. They key to being successful is trying to map out in one's head what the "end of day" chart looks like long before it actually takes shape on the chart.

The majority of traders were fooled by the Wed/Thurs big swings. These are people who are seasoned traders, not beginners.

Before I describe the events on the chart, I need to define two terms. The ES futures market runs nearly 24 hours/day and is composed of two parts:
1) Cash ("Live") Market - This is the time floor traders at the exchange actively trade the market, 9:30am - 4:15pm EST.
2) Globex Market - The time outside of Cash Market hours - from the afternoon through the next morning until the Cash Market reopens.

Okay, so looking at the chart, Tuesday was a normal day and ended down. During the Globex session, the market rose slowly but steadily. Then we get to the Cash Open on Wednesday, and the market starts moving down. During this time all the Twitter message traffic shows traders are going long, buying as the market is dropping, thinking that the market is going to resume moving up. The market keeps drifting lower, but people still keep buying. At this time there is hardly anyone mentioning going short (selling).
As the chart shows, the market was basically a one way trip down and those who bought now had to get rid of their positions with losses, then they would buy in again at a lower level, only to exit that position with losses as well. They never considered reversing and going short instead.
Some who bought at the start of the day and held their position, starting feeling lots of pain later in the day with mounting losses until finally, they close their position with a big loss. This is why you should use stop loss orders to keep small losses from becoming big losses. Unfortunately traders including me don't like using stops because the market tends to seek them out before continuing in the planned direction. But big market moves like on Wednesday/Thursday show why not using stops poses such a big risk.
So the cash market closes and continues to drop during Globex before slowly starting to rise before Thursday's cash open. At this point Bulls are very jittery and Bears are licking their chops to short more when the market moves up. A lot of the same people who were trying to "buy the dip" on Wednesday are now shorting the market rally, expecting it to fall back down. As the really continues, they exit with losses, and short again higher, only to close with losses as the market moves higher.  The Twitter traffic is the reverse from the day before - lots of people selling, very few buyers. Instead of reversing their mindset to buy, they keep selling. Towards the end of the day the market climbs at a faster pace, giving enough pain to sellers to force them to close, which adds pressure for other sellers to close, otherwise known as a "short squeeze". The market zooms up and makes up all the ground it lost the day before, as if Wednesday never happened.

Summary:
Wednesday: Market falls but majority is tricked to thinking it will go up and wind up losing. Bears are giddy with delight, and think market will be falling further the next day.
Thursday: Market roars back, but the folks who lost money on Wednesday are not likely participating because they are too nervous and wounded. The Bears who stayed in thinking the market would keep falling lost all their profit. New Bears who shorted today and stayed in lost their shirts with big losses.

You should find it fascinating that so many seasoned traders were tricked into doing the opposite of what they should be doing. This is what makes trading difficult - the market send out signals that are meant to confuse the majority of traders, despite their preparation.

How did I do? Well, I successfully got the bulk of Wednesday's down move, but even though I expected Thursday to be an up day, I got left watching since it never pulled back to what I was expecting as a low risk entry point. I can live with that, and I'm all kinds of glad I wasn't lured into trying to short this market today...it was a beast in the up direction!

In terms of the potential gains or losses made by traders - they were amplified by the big size of the swings: a 40+ point range! So for example, 1 ES contract gives you a $50 gain/loss with every point move up or down respectively. So a 40 point swing represents a $2000 gain/loss depending if the trader had a winning or losing trade- and that's just 1 contract. So you can see if a trader had many contracts and was wrong, things could get ugly fast.
In a worst case scenario a trader would be long on Wednesday and stay long, getting big losses. Then they would try shorting the market Thursday and wind up with huge losses again. The size of these swings could easily break an account - which is the risk all traders face. On the other hand, the trader who is on the right side can get tremendous gains. Therein lies the risk and reward of trading. It's not easy, you can lose big if not careful, but the potential is also there to make life changing wealth.