As long as Google's algorithm is trending in the correct direction (that is towards better quality results) then these complaints are just growing pains and I don't see much of a problem.
Some startups are criticised for simply being features of a chosen platform. Once they get big enough, the platform in control will simply add the feature and eliminate the startup. I'm unfamiliar with Nextag but it looks like a price comparison site and you could perhaps argue that price comparison is simply a missing feature of Google.
As far as I can tell, it's largely a bunch of spammers trying to attack Google for downranking their spam.
The argument is that Google competes with them and so shouldn't be allowed to use its dominance to favor its own service. But it's pure nonsense. These companies aren't valid search results. They only ever got into the results through SEO, and then they wail when the algorithm improves to kick them out. Someone who searches for "kitchen table" is looking for a website selling or providing information about kitchen tables, not a search engine that allows them to search for websites selling or providing information about kitchen tables. The user is already on a search engine -- other search engines are not relevant search results unless the search term is in the nature of "XYZ search engine."
What the complainers are doing is the equivalent of going into the largest chain of retail stores and putting boxes on the shelves labeled with a brand that the major retailer doesn't carry, which don't actually contain any product but instead contain a map to other stores that carry the brand the retailer doesn't. And then complaining when the retailer doesn't allow the spam products to remain on their shelves, and claiming it's an antitrust violation because the retailer has the most market share and it sells its own competing brands of products.
Naturally that doesn't convince judges or sell newspapers, so the spammers scour the world for instances of algorithmic imperfection that give a bad ranking to someone else, who unlike the spammers didn't actually deserve it, and then play ominous music as they reveal the shocking fact that some Google engineer's 20% project or some little-known subsidiary responsible for 0.00043% of corporate revenue arguably competes with the disadvantaged website in some fashion.