Fenixp: They do? Huh, I've never even heard of the site. My ignorance doesn't mean they're not popular of course.
I know about them because I read two of their other websites several times a day - Gamepedia and Minecraft Forum (I'm currently addicted to Minecraft :). They also have a popular YouTube channel, where they're making boatloads of money from advertising.
IMO, Curse is a pretty useless site for me as I don't play usually play games with mods or add-ons, but they are one of the top 5,000 websites in the US, and Gamepedia and Minecraft Forums are hugely successful as well - Minecraft Forums is one of the top 1,500 websites in the world and that means HUGE amounts of money from advertising.
If I remember correctly, they were named as one of the fastest growing companies a year or two back, and they seem to have gotten even bigger since then.