I like having house guests but what always gets me - whether it's friends or even family - is the basic lack of respect for another's space and things in said place. A host shouldn't have to be subjected to house maid duty to pick up after guests. The guests should appreciate the room and board, should pick up after themselves and mind the house rules.
My brother and my nieces (4 & 8) came to visit. They were little monsters. Leaving the fridge open. Taking handful of DVDs off the shelves and leaving them around the house. Leaving food around the house . . . and it goes on. And then he got ticked at me when I told them they weren't allowed to touch *anything*, period. Screw that . . . Last time they did this, they left everything as is and I was cleaning up after them for weeks - including some painting touch up and I'm still looking at a bright red cranberry juice stain in one of the bedrooms.
I don't mind general disarray (towels in the bathroom, jackets on the couch, shoes in the hallway. . .) because we're anxious to be out and about with the limited time they're visiting, but please . . . the rest is just disrespectful and shows a lack of self discipline if you ask me.