How'd they pull it off?

1) Tinder initially launched to college campuses

2) Tinder is a novel mobile implementation of an existing, familiar paradigm

3) Through association with strong positive emotions, Tinder creates evangelists out of heavy users.

In that sense Tinder is like WhatsApp and SnapChat and Instagram.

They create evangelists out of heavy users, too.

Note that a product does not need a lot of evangelists to spread:

Tinder claimed in May to have produced 50 million connections — if even .01% of those connections evolved into substantive relationships, 10,000 people may have been converted into evangelists of the product, proudly and openly praising the service as the catalyst of their relationships.

Isn't it notoriously hard to make venture-backed-company money in the dating space?

Yes but it's perceived as easy to make money in mobile if you have engagement. 

Examples: Facebook, Twitter, Whisper, Skout, WeChat, Paper, WhatsApp, Evernote.

Get mobile engagement and you can make money regardless of the space.

Through targeted ads and/or for-pay add-on services.

So if the money is all in building mobile then what's left for a traditional PandaWhale-like platform?  Or is there plans for a PandaWhale app already?

There are plans for a PandaWhale app. Working on it.

Those are probably the same reasons cliqie.com is spreading through my campus like wildfire