Solar Powered Trash Cans?

This is something I've always been a a little leery of.  I like the idea of integrating solar power into every day life, as well as the idea that individual should devices create their own power and reduce the stress and demand on the larger power grid.  Solar powered traffic signs on the highway are a good example of this, especially because they are portable.  A solar powered sign replaces a gas-powered generator or connection to the power grid to illuminate the sign, this is good because it lowers demand for electricity from nonrenewable sources.  

But the solar powered trash can is a bit different.  It's adding electricity to something that hadn't been powered before.  It creates an admittedly off-the-grid demand for electricity where there was not an on the grid demand before.  And what for?  Compacting your garbage.  

What's the benefit here?  Does the city save time, money, and energy because they have to empty the can less often?  I guess that's good, unless it's putting some poor slob from Southie out of a job! 

These things have been popping up all over the metro area for years now and I wonder what the return on the investment has been.  I also love finding that some are either located in near-permanent shade or oriented with the solar collector facing north!