they would need to also include the specific domain extension for it to be applicable
Yes, if the brand is "Apple" but perhaps not if the brand name is sufficiently unique (Wikipedia; TripAdvisor; Verizon).
A mega site is the NFL team.
I think the distinction between "brand" and "mega site" might be important -- and easily missed, since these concepts tend to go hand in hand.
If sites like suite101 and eHow were the intended targets of Panda, Google needed to identify "name brand mega sites" and to carefully distinguish those sites from the other extremely large sites -- the ones that are mass produced by content farmers.
So, it seems plausible that they might try using some sort of calculations that compare the number of pages on a site and/or the volume of traffic to the site with the number of times the name of the site is mentioned on the web or the number of times users use the domain name (with TLD) as part of their search.
For instance, perhaps many people use Google to search for "Dallas hotels TripAdvisor.com" in comparison to the analogous, smaller number who use Google to search for "how to choose the best Dallas hotel eHow.com" or whatever the closest analogous search might be.
The point being that there might be a huge discrepancy in search volumes including the domain name when compared to other relevant data, like the number of pages of content residing on the respective sites, or their total traffic volume. If the relative magnitudes were used (focusing on some sort of ratio, rather than absolute numbers), they might be able to push TripAdvisor and Wikipedia up while simultaneously pushing eHow and suite101 down.
Perhaps this might help explain why some branded sites are doing better post-Panda while others are not -- the important consideration isn't simply whether it is a branded site, but specific data and calculations that are correlated with brand names, but not perfectly correlated.
Panda is all about putting the highest quality sites first. Sites, not pages
I agree this is the goal, but that doesn't mean they are succeeding. In many niches the quality of the content on the name brand Mega Sites is limited in various ways -- it isn't really bad, but it may be too superficial or too biased, and thus not as useful as the content offered by a hobbyist's site, or by a smaller specialist site that no one has ever heard of.
I do think everyone needs to realize the rules of the game have changed -- you need to worry about quality and whether or not you can compete in that regard -- not merely whether you have better SEO, or whether you can crank out more pages than your competitors.
And, I don't think we should get too discouraged by the trend toward pushing name brand Mega Sites higher in the SERPs.
There is a limit to how far Google can go in this direction without undermining their entire
raison d'etre. People need search engines to find sites they don't know about; they don't necessarily need them to find sites they are already familiar with.