I think that we have to bear in mind that "inspiration" for a collection can come from a trend report, so when you see several houses using the same color palette, textile, silhouette within a season or over a season or two, then that is usually at play.
Zara is a retailer and not a designer and they wholesale copied some of Miuccia Prada's SS 2011 designs because, unlike other stuff she and other designers have sent down runways, the clothes were wearable and accessible, now if they are going around and calling these items, Prata or Paarda, that is an issue. Affluent people are not the only ones who set the trends and I would not be surprised if the retailers who already carry Prada may increase their orders based on Zara's copying of Prada. Most importantly, this solidifies Miuccia Prada's position as a directional designer.
Let's play this out using Louis Vuitton as an example, because quite a few people observed common themes in their FW 2011 collection with other recent and contemporaneous collections, although bear in mind that that may be the trend report phenomenon. OK, if I am a small to mid-size designer and I send something down the runway that Zara copies, as has been stated they are pretty blatant with their copying so the connection is going to be obvious, some smart blogger is going to pick that up and do a sneering post about it, right? That is just increased name recognition, and if the copying is covered enough and buzzed about, I would be willing to bet that the next season there will be more editors and more important editors at the next show, which increases the odds of being featured in an ed or them doing a blurb about the collection /designer and hopefully, eventually increased interest from buyers. Actually, the Zara copying may have directly led to increased interest from the get go. Didn't this to some extent happen when Phoebe Philo was at Chloe?
Now if Louis Vuitton, the largest design house within the largest conglomerate in fashion, appropriates the ideas of another designer, it will get noticed and discussed in the blogosphere, particularly on sites like this but will it get picked up by the mainstream fashion press given who is buttering their bread? Will the ire over the similarities be able to transcend the

because Naomi, Kate and a slew of other model faves walked the show and the

and

because JLo may be doing the campaign? When you pick up a Vogue, whose ads do you see on the first few pages and therefore which design houses do you think have a better shot at being editorialized? Therefore a small-to-mid-size designer may benefit more from Zara appropriating its designs than a larger designer who caters to the same market, and yet it has considerably more resources, connections and recognition.
What Zara did to the blogger was not right, and if she has grounds for legal action, she should sue, did she? I don't condone what Zara did but that did get a decent amount of press / blog / message board coverage and I betcha it raised her profile considerably, that does not make it right but I am just saying that there is a silver cloud. This is kinda the point that I am making, if that photo was considered a good representation of cool, then there is a chance that a savvy blogger with a bigger following will appropriate the vibe into their own street style / 'look at me' images, and since some bloggers these days get invited to fashion shows and are even consulted by muckety-mucks in the fashion industry, there is an incentive for them to try to appear leading edge, and if the inspiration is not coming from within, they may look elsewhere, including lesser known bloggers.
* Although I don't think that this is not a small blog, but I don't think that it is one of the biggies either.