You should only get things signed for personal/private collections...getting a heap of 5c cards signed to sell for $10 each on ebay is money grabbing.
As already suggested...good manners cost you nothing.
These people owe you nothing...stop pretending they do.
If you don't know their name...don't ask, don't speak, and avoid an awkward moment for everyone.
Don't wear a Storm jersey when you're asking for a Manly sig.
Be courteous, co-operate (players and fans), consider (others), and use your common sense (although, not easily recognised by many).
That's my two cents worth...