I'm looking at Josh Utter-Leyton's Bant deck[/URL] which has some similarities to my own, but he has these Verdant Catacombs in there. What does he need it for? Is there some sort of metagame in modern that necessitates it? He doesn't even have a swamp to pull.
Is he just going slightly off-color with his fetchlands to thin his deck out?
Only half of the fetchlands were in that Standard format. The "enemy" fetchlands were printed in Zendikar block (UR, GB, UG, WR, WB) and are legal, while the "allied" fetchlands were printed in Onslaught block (UW, GW, RB, RG, UB).
If you're playing Bant, there are three 2-color combinations in your deck: UG, GW, UW. Only one of those three color combinations has a fetchland that's actually legal in that environment: UG (Misty Rainforest). Because of the interaction of fetchlands with Lotus Cobra and Knight of the Reliquary, it was worth it for him to run off-color fetches. And since green was his predominant color, the GB fetch (Verdant Catacombs) was the correct choice.
We see the same thing in Modern, where sadly only half of the fetchlands are legal. If you're playing a 3-Color "Shard" deck (UGW, GWR, UBW, UBR, RGB), only one of your color combinations has a fetchland available to it. Fortunately, because of the way that the basic land types work on the Ravnica shocklands,
any fetchland that that has any one of the three colors can fix for any single color in your deck. You'll often see Jund decks playing Marsh Flats, for example.
I'm not a mana-base expert, but I'm pretty sure this phenomenon is one of the main reasons why we see UWR decks so much more successful than Grixis or Esper decks in Modern.