Pollution and Corrosion
Solar panels are quite susceptible to corrosion -- which is one reason they are built in clean laboratories under the strictest of conditions. That said, the smog and corrosion of major cities can very quickly lead to a rapid decay of even the best solar panels.
However, even with this accelerated decay, solar panels will pretty much always last long enough to pay for themselves -- and then some.
As alluded to in the first section, latitude has everything to do with optimal solar performance. The closer you can get to the equator, the more sunlight you can collect and the more power your solar panels will produce.
Additionally, these solar panels need to be south-facing. A major disadvantage for solar energy production is that most of our roofs are not southward-facing. That means that many homes have to mount their panels in their yard, and take away from their precious living space -- something a lot of homeowners want to avoid.
That said, a lot of homeowners are ignoring the disadvantages of solar energy and ridding themselves of a monthly electric bill by going solar. In addition, new technologies are being capitalized on which allow solar powered plants to store heat and produce electricity all night long!
If we could just find a way to put more resources into solar technology and get its cost a little bit lower, it is likely that we would see fewer posts and questions about the disadvantages of solar energy and more signs saying "go solar now!"