Runescape Member Card Scams
Jagex may have prevented many ingame scams through modifying the code, although some people may have been scammed into buying fake or unusable runescape membership cards.
To avoid any scams you should know whether they are available in your country or not. At the time of writing this post they are only available in USA and UK (meaning they only work for UK and USA players). If you don't live in UK or USA then check the main runescape.com site before ever buying a card.
The normal cards are for 30 days or 90 days. These can be bought from various different stores throughout USA and UK. When the cards are available in other countries Jagex will make an announcement on their site.
Some reputable stores do sell the runescape membership cards online - although I do not use the prepaid cards myself.
For 12-month cards, I think the only place you can get them from is the Jagex shop itself (this may change at a later date, but only ever buy the 12 month cards from the Jagex Store to avoid any scams).
The EU store (uk cards) is at Jagex EU Store
The USA store is at Jagex USA Store.
Happy Scaping - enjoy your runescape membership card