This is some speculation on my part, but here are some points to consider. This is an interesting question, and I'm throwing out ideas on both sides of the argument to see if other people have counter points or alternatives to think about.
Why would the specialist or some other player show his hand on a big offer like that? All of the traders that I know who do very large size are quite careful about *not* showing that size so they won't crater the price if they are offering that much out. I think the specialist will show size in a stock if the trade's about to be done. In this example, he'll show the size on the offer, then print against it. As orders come into the specialist, he will execute these against the orders in his book, and the larger they are, the more it will appear that the price is "moving towards size." If the price is hunting around during a choppy time of the day, then it's possible that once that large size shows up in the level 1 quote, it will scare off or absorb any small buying interest at that point in time, so the stock *may* sell off a little.
If another trader's showing large size on the offer, he or she may be trying to influence the stock's direction. That person is probably already short (and clearly willing to risk being short more). Now, if someone really knew which way a stock was going to be trading, why is it necessary to to try to influence it with a large offer?
That size could be a resting order sitting in the specialist's book. The owner of that order may be playing on a different timeframe than others are. Would I be willing to try to participate in a bounce off of this size? I guess it depends.
Two weeks ago, in a large afternoon sell off, I saw 500K shares come up on the bid at XX.15 in JPM. The market kept selling off, and the half million to buy kept getting refreshed. A ton of prints went off at 15 cents, and after something like 10 minutes, the bid was finally taken away. Guess what JPM did? Freefall..... Because the market and all of the stocks right near JPM were selling off, I wasn't willing to go long that stock even though a very big bid showed up.
