that is already factored into the price. Note the P/E of such internet retailers. Getting all into this is similar to convincing yourself that buying heating oil futures before winter will make you rich. Seasonal factors area already factored into the price.
But don't you know - do you know of any reason why a stock should have a 105 forward pe versus a 140 forward pe if growth %s are only in the 20-30% range? I don't. Furthermore, tons of stocks (look at CRM) have prices that have escaped forward PE / PEG standard valuation models *for years now* and have made horrible shorts. Personally I'm not running out and buying these stocks, but its fair to say they'll appreciate if the broad market appreciates. EBAY is a better buy... AMZN... ugh.
if you know the game of poker, you'll realize anytime you start all IN, is when you lose all your money. only time when you all in, is when the other guy has $30, and you have $500, All in, what the hell , just saying the phrase is fun but won't ever hurt you. You'll be burned.