I don't think viral effects alone will be enough to turn the project into a sustainable startup however. The current value proposition of "see how worldly you are" doesn't have me reaching for my wallet anytime soon.
All that said, WhereMyFriends.Be was truly a fun web app that we wanted to put out there. We made it for ourselves to see if we could do it, then when we thought other people would enjoy it we started making it public and releasing it. As of now, we still have no intention of making it into a sustainable business [unless any of you have any suggestions...]. We are just looking to have a little fun, and give people a fun thing to play with.
How much other press did you get? When i look at at site (and a lot of Gen Y) I look for at least 3-4 pieces of "social proof"...Mashable would definitely be one, but i am looking for a handful other before i "buy".
If i were you i would use the Mashable effect to parlay it into more press at other small/medium size outlets, That is how you could really get the most value out of the hit.