You can preach all you want about only recruiting people you know, but then how does the game have a chance of growing? In short, you spy because you don't care about the future of the game or you are too stupid to realize how it effects an already dwindling player base.
Full of win.
Most experienced players are aware that spies aren't the end of the world for our alliances, and I'm sure most people soldier on regardless. Personally I like a good challenge in the game and fighting against the odds is when I have the most fun. So for me they will never have a massive effect.
But that doesn't mean I'm willing to overlook the effect they have on the less experienced or less active alliances. The sort of alliances who right now fill ranks 5-10. A spy for them can be devastating as the top alliances will target them specifically, knowing they can get easy land, and with a lot of their players not being as experienced they can lose hope and end up either jumping ship or quitting altogether. And if a few members do this it can quite easily spell the end for the alliance.
So because of this I'll never use spies, I'll never accept ID lists from people before spies are out, and if anyone posts spy intel on politics I'll delete it. It is a scummy tactic which only cowardly idiots use to gain a cheap advantage because they can't compete fairly, and I'll always despise anyone who spies or uses spies.
But by all means carry on with your "It's not against the rules so I'll keep doing it" attitude and continue damaging an already small playerbase in your pettymindedness and ignorance.