If what you said was true the exchange rate would have collapsed in the last 2 years (BitPay and Coinbase accumulated 60,000+ merchants who began accepting Bitcoin over the last 2 years and most of them automatically convert BTC to USD). But instead, the exchange rate rose from $10 to $580:
http://bitcoincharts.com/charts/bitstampUSD#rg730ztgSzm1g10z...Why? Because as Bitcoin is accepted in more and more places, it increases its subjective value, so more and more people are looking to get some bitcoins, which counterbalances the downward selling pressure.
