Re: In a word: YES
"Quick show of hands. How many El Reggers have been invited to work for free after pointing out faults and flaws in company websites?"
I'll go you one better. After declining their offer to discuss a security issue I discovered with a site's dev guys, they threatened legal action. Basically "help us fix it for free or we'll have the cops nab you for hacking".
I politely declined that little offer too.