Put simply: It matters because taste is not the only criteria used to select which seafood to buy.

One might make a choice based on mercury content, environmental friendliness, dietary restrictions (medical or philosophical), to support (or abstain from supporting) a particular industry, or something else entirely.

To allow fraud which can't be detected on the palate is to deny buyers their freedom to choose based on any criteria other than taste.

It is not up to the producer what criteria buyers use when choosing their purchases.

Also, if the consumer shouldn't care, the producer shouldn't either. If the producer thinks it shouldn't matter what it says on the label, well then... no harm in putting the right thing on the label, right? No? I guess it matters then.

Of course it matters, you're being defrauded as a consumer.

Aside from that, it could have health ramifications. Most people eat organic to avoid herbicide exposure, and most people use olive oil because it's considered healthy. Obviously there are countless examples. You should get what you pay for.

  Here's another perspective on it, how often will you notice? If you don't then does it matter?

A few years ago I purchased some olive oil while overseas from an outfit that was literally running a large machine pressing olives in front of me.

Shocking, the oil actually smelled like olives vs the stuff in the bottle, which usually smells like nothing. That oil also had a sharp olive taste which is actually missing from the store purchased stuff as well. There is a bit of an olive oil industry starting in texas as well, and that stuff when purchased directly from a farm (orchard?) tastes like olives as well. Makes me wonder if 100% of the olive oil i've been purchasing in the last decade is fake, or per some of the articles strongly cut.

BTW: Its not a function of the age either AFAIK, I purchased nearly a gallon when overseas and it lasted me over a year, all the while maintaining the distinctive smell and taste.

"Olive oil" by nature (without even getting into fakes) has a fairly wide expected gamut -- extra virgin, virgin, refined, and pomace oils (all of which but the last can be marketed as unqualified "olive oil", though in practice that generally mean either refined or a blend of mostly refined and some virgin.)

A place that is doing something like artisanal premium extra virgin olive oil (which is what it sounds like you were getting) should have exactly the relation to generic "olive oil" that you describe, even if nothing involved is fake or adulterated in any way.

Which is not to say a lot of what you are buying as generic "olive oil" might not be fake (there's plenty of independent reason to suspect that), but what you describing doesn't really indicate that.

The whole deal with food regulation is it's very hard for a consumer to test for toxic substances/purported nutrition etc. It absolutely matters even if you don't notice.

This is talking about the identity of fish though, I'd guess that this is not talking about the toxicity of the meat. The article does mention that they are certain species which are known for higher toxic chemical contents, so that can be an issue.

However, isn't the toxicity of the meat is a separate issue? I have no idea how the FDA tests for that (sample testing?) but it probably isn't just discrimination on the species of the fish.

It's highly correlated to species of fish; some species have much, much higher levels of toxins such as mercury, depending on where they live, where they are on the food chain, etc. You can't separate the two.

It matters because its the consumers responsibility to know what they are buying. Obviously for a consumer to do their due diligence a product must be what is claims to be.

As the article said, the mercury content of different fish can be a very big deal for certain people (especially pregnant women).

That is a good point, when it is a health issue related to the type of species, I can agree. That seems like a regulatory issue and the FDA or other regulatory agencies should care.

It matters for organic food, because people buy organic food for ethical reasons that don't necessarily have any relationship to quality.

"Do you care" seems easily demonstrated by what you thought you ordered.

If I don't care what kind of fish I am getting, I order fish and chips, or fish tacos.

If I care what kind of fish, I order tuna or eel or salmon or trout...

Escolar substitution is a definite cause for concern, due to its laxative effect.

Escolar contains a natural wax ester that can cause digestive distress and diarrhea for days.

It's been banned in Japan for 40 years.

The USDA banned it in the 90s and then unbanned it in 1998.