Darwyn Carson, the Romulan Tal Shiar operative was never even given a name, probably because in her episode of Star Trek: Deep Space Nine (go figure), she only gets about 3 minutes of screen time. Why then do we care about this character?
First of all, just like we're in awe of the fact Gabrielle Union played a Klingon, we're in awe of Carson's portrayal of a Romulan. Romulans are no joke. They have the sharp intelligence and strength of Vulcans, and they're dedicated soldiers of an empire, like the Klingons (whom, ironically, they happen to thoroughly despise).
Secondly, Carson doesn't portray just any Romulan, but an operative of the Tal Shiar (*shivers in delight*). The Tal Shiar are like the NSA, CIA, and FBI of the Romulan Star Empire, all rolled into one...plus a whole lot more. This is precisely why whenever the writers on Star Trek needed a really good episode about espionage and political intrigue, they often employed the Romulans as the central characters. When it comes to cunning, mystery, back-stabbing, and overall bad-assery, they could never go wrong with the Romulans.
So you can see why we're upset.
I mean, we had other recurring operatives/ex-operatives on the show: Garak, from Cardassia's Obsidian Order (played by a white guy), whom Carson's character tried to have assassinated (oh, irony). And Sloan, from Earth's Section 31 (also played by a white guy). We had no recurring operatives from the Romulan Tal Shiar, and you're telling me we couldn't have had Carson guest-starring every so often, kicking some ass in the shadows? Seriously?
Carson doesn't even suffer from Ilario Syndrome. Her character suffers from Robau Syndrome, as in "not enough character to even study."
*sighs and shakes head*