I saw this on reddit a few days back, and showed to family members who are less technically inclined and hopelessly addicted to facebook. It seemed to hardly bother them, as they continue to use it the way they have been - shaping their life choices based on the chosen moments of others' life. What concerned me was they found the advertisements "very useful", as it reduced the time spent searching for goods they wanted to buy. I haven't been able to put up any argument convincing enough about why this trade off is bad.

Metaphors, I think could have a better result. One that I have thought of is: If this was a job position, and one candidate could buy their chances of getting picked - would it be fair to the other candidates or the company? It only profits the broker.

Any other convincing argument I can put forward to get them thinking about it?

Ultimately, all arguments come to the fact that "keeping in touch" is so much easier with facebook - and I do not have an alternative that I can propose. Note I use the word argument as any discussion I have tried to initiate becomes an argument very quickly.