If anyone's not aware of what dark.fail and darknetlive are: They index the onion addresses of hidden services, mostly dark net markets (à la Silk Road). These are useful as the onion URLs can be difficult to discover/memorise, and best security practices when using them involve using a clean OS each time you connect, so bookmarking is not always trivial. dark.fail especially has built up a reputation for keeping correct and up-to-date links, so many people just trust that the links listed there are correct without checking. A compromise of such an index could allow scammers to easily phish customers of these markets, or law enforcement to harvest customer details.
Edit: Looking further into this, Darknetlive is apparently already serving phishing links according to a signed statement from its operators. I would imagine quite a few people will be caught out by this.