Nearly every startup ends up with a list a mile long of potential features, ideas, refinements, communities, partners and revenue sources. Being able to pick out the right few to work on (and what to say no to) is maybe the most important skill a startup CEO can have.
A founder who has been around the same space for a long time can use past experience and intuition where a newly-minted CEO knows very little and is actually best off when they recognize that.
Per Crunchbase[1][2]:
In 2008, Gowalla raised $2m, foursquare raised nothing. In 2009, Gowalla raised $8.29m, foursquare raised $1.35m. In 2010, Gowalla raised nothing, foursquare raised $20m. But by the time this happened (June 2010), the "check-in wars" were over (e.g., see: http://techcrunch.com/2010/07/07/foursquare-gowalla-stats/).
[1] http://crunchbase.com/company/gowalla [2] http://crunchbase.com/company/foursquare
[1]The article says 2009, wikipedia says 2007?