Selection bias

Job quality improves during crisis, wages rise.

Selection bias.

Bad, low wage jobs disappear.

Minimum wages - a logical ground

The economic literature on minimum wages is immense. I won't address this here. Yet there is one simple argument for minimum wages: there exists some kind of wage that is the necessary minimum for a worker to reproduce the workforce. It makes no sense to pay anyone below the level of what is necessary to raise a child. If you did, in one generation your economy would be doomed. This has happened before, as is documented in Marx' Capital.

Of course, if one's market price is below the minimumwage, subsidies may be an option to get this person employed, lowering effectively the taxpayers income.

Here's a random newspaper opinion on the matter: http://www.citylimits.org/news/articles/4571/half-of-recovery-jobs-offer-low-wages-so-raise-them#.UdFhfzsqz64.