Six months later and those fakes are still out there on eBay! Got stung, got refunded. Two words for you: 'Trading Standards'. Last I heard, they were thinking about raiding the guy...
Sandisk cards are so much cheaper than they used to be (got a genuine 2gb Extreme III card for £17 the other day from a reputable on-line dealer) there's no point taking the risk. The OEM 2gb card I bought last year (and shoved into an abandoned iPod Mini) cost me more than twice that!
PS The above guides on spotting fakes still hold true, but you can also call up Sandisk and have them run the serial number through their computers.