Most band's second albums don't live up their first, I reckon (with some honorable exceptions such as Radiohead). Probably because after an album release a band spends ages touring and working and doing interviews and stuff, and don't have the same focus or time they had before (this is just a theory - I'm sure it's different for many bands). Or, because they only had one good idea to start with, and played it out fully in their first record, or initial burst of releases (see: The Hives, Franz, Strokes et al).
The pop-buying public is more fickle than ever (look at their U-Turn on The Darkness - heroes to zeroes). Internet means people can cherry pick the best songs and largely ignore albums; the glut of new soundalike bands means there is always someone new to be into 5 minutes after you're sick of the last fad.
Are music careers destined to get shorter and shorter? From one-hit wonders being the exception, to one album wonders being the rule? Will this effect force musicians to try harder to evolve, change and adapt? Will it drag up the quality of songwriting so albums don't contain disposable filler? Are the days of the 'album' format coming to an end? I'd quite like to see bands release more on a regular basis rather than a slab at a time.