I hear over and over again that it is illegal for the MM to manupilate stock prices, but we continue to hear more and more stories of illegal stock manipulation. Here is a recent post from an individual trading GRZ which I found interesting which seems to support that it does and continues to occur:

"Did anyone notice that the share price started the move upwards just before closing time of US markets? Continued until what I presume is the Canadian brokerages taking the manipulation over. When I saw the move at about noon I placed a 1000 shares for saleat about 13:14, some of them got sold but the majority remained because the upper price range stopped at my price 5$14C and an ask appeared for 100 at 5.13. That is where my broker Questrade ( actually Penson) took over and dropped it to 4$96C.

The price having been lowered sufficiently I decided to play the game. Placed a buy at 5.01 but before my bid was displayed ( they seem to have delayed my bid for about two minutes ) they placed their own at 5.02. I up to 5.02 they to 5.03. I removed my bid and theirs disappeared also. Did that a couple of times until I left it at 5.02. Guess they realized that I was not going to go anywhere but wait to pounce, they finally sold me 300 at 14:24 but did not show it until 14:45! Is there better proof of manipulation? I do not think any better is needed. Now consider where the share price would be if it were not for the heavy handedness."