Snow Covered Lands

[Jay]

Anybody know why so many people use them?  I've seen them in net decks for T1 and T1.x decks without and cards that rely on them.  I know there's no down side to them (unless someone plays some weird ice age or coldsnap card, which I've never seen happen in a tourney), but with so many people playing them I wonder if there's some benefit that I'm missing.

[Nefarias]

It mostly started back when Gifts Ungiven was unrestricted and became popular. While not unheard of today, back then it was a fairly common play to search for four mana sources with Gifts. Since Island and Snow-Covered Island have two different names, it gave you more options.

For a small time, seeing a Snow-Covered Island from your opponent was a good signal that you were facing Gifts, even if nothing else had given it away to that point. So then non-Gifts decks started putting them in as a bluff. At that point it became pretty standard.

So the only actual application today, as far as I can tell, is for the fairly small percentage of cases in which you would want to Gifts for it. Any sort of psychological advantage at this point is probably irrelevant.

[Mr. Fantastic]

Snow covered lands have synergy with Tainted Pact and defense against Wake of Destruction, as they count as having different names from basics.  Not that anyone uses Tainted Pact or Wake of Destruction.