Jamawani, I am sorry to hear it. Warmshowers is a wonderful resource, and it distresses me to hear of people abusing it. And when they do, they should not be encouraged. You did the right thing to turn these people away; perhaps they will decide Warmshowers isn't for them.

I've had a couple Warmshowers tourists camp in my yard, which has been perfectly painless for me. And I've stayed with a few, which has been a really wonderful experience. In fact I'm planning a short tour for this weekend, again relying on Warmshowers; otherwise, I fear I couldn't do it.