Last weekend I went to watch Sporting Lisbon. I noticed a couple of interesting things. Firstly they had a massive poster right on the side of their stadium which basically had an electronic tally of tickets that were sold for that game. I think the poster translated to something like, "Are you going to stay outside or join every one else inside and get behind Sporting?"
Also when I tried to buy refreshments inside the stadium, you had to buy a card/voucher (of various amounts) and then use that to pay for your items. This would firstly stop people handling as much cash as there would be only a select few people who sell the cards, also people may leave money on the cards and therefore the club may make some extra profit as away fans will obviously throw them after the game.