I enjoy giving my opinion, when it comes to customer surveys. Especially when I get something for it, be it a discount off my bill or a gift from that company.
Telemarketers are pond scum, scraping desperately to anyone with a pulse to buy into their product. Especially when you have no intention of buying, offer a pllite 'no' yet they still persist to try and convince you. All those hurdles are in front of them before they call, right down to the exact words to say when someone politely says 'no'.
If theres anything to be learnt by this, simply hanging up the phone may not be enough to deter telemarketers, unless they are very clever and mark you off the call list for 'gadgets' but keep you on for 'household products'. They're slimy bastards.
Here's one guaranteed way to kill off these guys. Turn their product against the call they are making. Make the product evil in the telemarketers eyes, and conscience will take over. Learn from a great comedian. Listen to this recording (in Ogg format) before Dec 27 to get an idea.