Might be worth investing £5
for the fun of seeing some hacker get a vacation in the slammer.
I could imagine getting some debit type credit cards, loading them up with £5 each, setting up some e-mail accounts under various usernames, setting up some Amazon or other on-line vendor accounts using those same usernames, and deliberately using the same username / e-mail and password on some other crap websites, and then waiting.
When some skript-kiddie get the credentials from the inevitable breach, he/she can order a maximum of £5 worth of stuff.
Chance of skript-kiddie being identified and getting caught? No idea, so don't know if this would pay off versus just losing the £5 quite often.
But if the chance of getting caught were high, it would be worth the £5 to see them get busted.
Does it count as entrapment if it is not the police doing it?