Not only that but Yelp "getting into" a new line of business or revenue stream does not mean you get to say "it's a $50 billion market we're getting into so clearly we can add $5 billion to Yelp's value!"
Until it's generating something (e.g. cash on the balance sheet or some other tangible benefit) I don't see how it would affect valuation at all.
Until it's generating something (e.g. cash on the balance sheet or some other tangible benefit) I don't see how it would affect valuation at all.