  We discuss the importance of including baryons in analyses of unified dark
matter scenarios, focusing on toy models involving a generalized Chaplygin gas.
We determine observational constraints on this unified dark matter scenario
coming from large scale structure, type Ia Supernovae and CMB data showing how
this component can bring about a different behaviour from classical
$\Lambda$CDM and thus motivate further studies of this type of models. We also
speculate on interesting new features which are likely to be important on
non-linear scales in this context.
