A new type of parking meter is going up in various cities throughout the US including Silver Spring. The meters collect coins for the homeless to provide funds to shelters and soup kitchens (see some pictures here). They also provide a substitute for those donating to give their money to the meter instead of the panhandler on the street. The meters also decrease revenue for pan handlers lowering the benefit to asking for money on the street.
One result is that instead of asking for money those panhandling may increase their use of shelter and soup kitchen services. Another possible result is that the relative payoff of petty crime may increase.
This could be a neat experiment for a city. Put homeless meters up in some part of the city and not in others. Also collect data from panhandlers (difficult, but I think doable). Do they move? Do people give more or less when meters are around? Does crime increase?
All sorts of things can happen. I don't think it's clear what the result will be if meters are installed in most busy places.