The point is that when you're looking for a toaster oven and your friend says that his coworker's spouse just got a ToasterGenius Model Z and they're happy with it, you can be fairly confident they're not shilling for ToasterGenius. They may not know anything about toaster ovens, and they may not have the same toasting needs as you, but at least you can probably trust that their opinion is genuine. Of course, I suppose it could turn out that ToasterGenius is running an MLM and your friend's coworker's spouse hosts ToasterGenius home parties to sell ToasterGenius products!
You probably know your friend well enough to tell if they know anything about toasters or evaluating consumer products in general, and whether their views and needs corresponds to yours. So you rate the recommendation for ToasterGenius Model Z somewhere on the scale from "my friend is a bona fide toaster expert / fanatic", through "my friend toasts as much as I do and is attentive", all the way to "my friend doesn't know first thing about toasters, and also doesn't understand the concept of communicating uncertainty about one's beliefs".
This kind of ability is what makes word-of-mouth within your social network super useful. On top of that, if your friend ends up purposefully shilling for a MLM, they're doing that at the risk of immediately burning your friendship.
(Tangential: MLMs are social cancer that prey on relationships between friends and family members; they should be excised from this planet.)
I'm not saying the point I outlined above is the best outcome for the world, it's just the outcome for me and it's pretty regrettable that we're sliding back into it.
Yes, in the context of a relationship. A "review" from someone one has some kind of relationship is more meaningful. Possibly a weak one, like a fellow HackerNews poster. Which brings back the Internet--helps one form new kinds of relationship.
Because "Word of mouth" over the internet would imply that The Internet still has a big role to play in disintermediation.
Would "reviews" from your network, any network, physical, or digital, of people you know, be valuable? I believe that a "review" is only useful if you know the reviewer well enough. Regardless of the medium.
For example, when "angry uncle Joe" rants about some libtard-foreigner-restaurant-scum which is ruining the neighborhood with their horrible foreign food, I know how to take that 'review' of the restaurant. Same when aunt Carol explains how she heard from the new boyfriend of the cousin of Foo that her brother said that she heard from.. and so on. But when a friend who knows a lot about fintech explains that SomeBank is really doing a lot of interesting tech and hiring, I also know how to take that.
If you know who the "review" comes from, you can trust it. Otherwise you cannot. I assume this comes down to "word of mouth", though.