Recently, the WMAP group has published their five-year data and considered the constraints on the time evolving equation of state of dark energy for the first time from the WMAP distance information. In this paper, we study the effectiveness of the u
sage of these distance information and find that these compressed CMB information can give similar constraints on dark energy parameters compared with the full CMB power spectrum if dark energy perturbations are included, however, once incorrectly neglecting the dark energy perturbations, the difference of the results are sizable.
