I have played many games online with all three species.
I have never actually been "embargo rushed", but I have done the rush several times myself very successfully.
Now, the embargo rush is simply defined as getting the sova carrier, giving it the 'embargo' skill and attacking your opponent's homeworld early, making sure to use the skill to hinder the OP's frigate construction and get a bunch of money.
This is enough to give you the edge necessary to attack directly.
But this is not something that can be directly countered because it does not contain a specific build order of fleet composition other than the sova.
What I do, specifically, is rush out two military labs while taking an asteroid, and then, after taking 1 or 2 'roids, send in the sova and the lrms I am constructing with the rally on the sova, given that I will not send the sova in until I have enough lrms in the making to fend off whatever my opponent has, or make sure that the sova wont be taken out in any event.
So, given that I make lrms to back the sova during the embargo rush, I put it on you to find the best way to counter this strategy. This is an incredibly powerful tactic, but certainly there should be a way to counter it.
I will say that if you just say "I will make flaks", then I will just "make cobalts".. Also, flaks suck at attacking cap ships and so wouldn't help you to take out the sova.
So again, what is the best counter to "the embargo rush"?