Scenario:
Team game.
You've got all but 1 country in a continent.
You surround that country.
That country is owned by your teammate.
Your teammate has more than 1 army in that country.

Since he has no means to exit, other than through you, either you have to attack him and hope to win, or he has to attack you, and hope to lose.

I know that the dice odds say that it's better to attack than to defend, but that assumes you're attacking with more armies than he's defending with.
Those odds change drastically when it's 2vs2 or even worse 1vs2.
I believe then, that the best team tactic is to have your opponent attack you with only 1 army.

But maybe my math is wrong, so can someone check me on this?
(I believe there was  forum post on this once before where someone stated their ideal teammate was one that did one of 3 things, the last of which was "attack me, but for god's sake only do it with one army," but I can't find that post)

You attacking your teammate, 3v2 you lose about .85 units per teammate unit.

Your teammate attacking you 1v2, you lose about .34 units per teammate unit.

Much better to have your opponent attack you 1v2 and get themselves down to one unit before you finish them off.

Here's the post you were thinking of, Boris: http://www.wargear.net/forum/showthread/1027p1/These_strategies_may_be_useful

Look at #12

That's exactly what I was thinking of, thanks ATH!