At the 4th Street transfer point between MUNI and Caltrain, five ticket vending machines provide their mechanical services to riders.
Correction: two do, but only one accepts bills.
One of the machines (CT-5) has been wearing an Out of Service sticker for more than two weeks; another (CT-2) has a fuzzy screen; a third (CT-4) had a handwritten "Out of Order" sign that came off yesterday, although the machine is still broken.
Which means that someone who wishes to purchase a MUNI ticket at this busy transfer point must wait in a queue for one of the two working machines; if you are in the wrong queue and end up in front of the machine that doesn't accept bills, you might well miss your train.
MUNI doesn't provide a convenient way to purchase single-ride tickets ahead of time: all tickets sold through vending machines are stamped with a 90-minute lifespan. Tokens are available for a reduced price ($1.05 instead of the full $1.25), but through select and obscure vendors only (tobacconists in the Tenderloin). They are not typically available at MUNI stations.
Although I feel a sentimental attachment to each of the varied shape of paper transfers MUNI sells, I'd much rather suffer through the availability and convenience of an electronic fare card.