The large packaging is inconvenient as hell (I usually end up getting a plastic reloader's tray and moving the rounds over for storage) but isn't any worse than anything else.
Styrofoam is mostly air. If you're looking at mass the mass is potentially less than other plastics in trays--if you weigh the styrofoam block and then weigh a plastic tray on a Cor-bon or PDX ammo tray I'll bet the quantity of non-air material is not significantly different.
Despite what the environmentalists might assert, ALL plastic breaks down over time (as well as most everything else except maybe glass). UV hastens the breakdown but even if buried and exposed to elements of any kind--heat, pressure, water, air, chemicals, etc plastic will usually break down.
I doubt the dinosaurs knew over millions of years they'd turn into something as valuable as oil either. We sometimes second guess the powerful forces of nature (and our total inability to control her) a bit much. This doesn't mean we should be wasteful or pollute unnecessarily--only that man has a far lesser impact on the world than he thinks he does.
An interesting bit of trivia is the composite sectional density of a passenger occupied airplane is actually close to what it would be if the entire volume were filled with styrofoam (but someone did this study 10 or so years ago so's it might be a bit different as people have gotten heavier).
But I don't like the packages either--they waste space IMHO.
Cheers