I've seen that happen, where a company upgrades a stock and blatantly tries uses that upgrade to dump it. I forget the stock, but about two weeks ago I heard over squawk that UBS had upgraded some company on the NYSE that is relatively thinly traded... the stock was up 60 cents, and what was holding it back was a big offer on guess what ECN? UBSS!
its amazing that they have the audacity to show what they are doing in plain view.they don't even try and hide it by using an ecn. there are times when an upgrade is an upgrade and the stock moves nicely. remember,one of the last things a short wants to see in the morning is a stock he sold short being upgraded. i made money yesterday by entering NGPS pre-mkt on the Needham upgrade and it worked out well.