Yes, there is simply no way that one can stop trading on the basis of insider information, or any kind of action that is based on non-publicly available information. The checks and balances are in place, as Don says, but there is still a tremendous number of actions that come from such knowledge. And bear in mind that these actions are usually quite heavy : they certainly don't involve no measly 100 stocks' transactions, you bet!

Add to that the tendency since the 80s to take down several barriers in the money markets that tended to prevent some of that stuff.

However, I did not include the factor of insider information when I claimed that the lone, individual investor is usually a loser against the big boys. I don't have to invoke that factor. The lone, individual investor simply doesn't have the tools and the education and the ability to properly distill the information out there. And I'm talking about the legitimate, publicly available information. (Oh, yes, we do have "all the information", as Don said. Actually we get loadsa information, tons of it! Let's have fun watching the Topeka day trader trying to make sense out of that pile.)