This is pretty interesting.

I tend to use my card wherever I can but that doesn't cover nearly enough of the occasions where I'd spend money to say that I don't need cash and so I usually try to have what must be about 15 USD on me.

Firstly, taxis only take cash and actually I think they prefer coins. On campus I don't think any of the food vendors take cards and while there are ATMs it's quite a schlep with queues and all.

Not to mention that most of these transactions are going to be like 2 USD so the POS card charges wouldn't be pretty.

Bars/clubs are another one - minimum card transaction is often about 6 beers' worth so obviously it's best avoided. I also don't think I've ever seen anyone pay entrance with a card.

It would be nice if something like m-pesa would take off because after all that, carrying cash is a bit of a liability. Some people are saying that they have like 40 USD which is a bit much for me to risk...

edit: my roommate informs me that he never carries cash (mugging risk), and that he draws money when he does need it.