Though consumer HD cameras are becoming more common, camcorder manufacturers have completely missed the boat as far as putting together a package that best fits the general consumer's needs. You can get a cheap camera now that will shoot 16:9 1080i high-def, and that's great, except if you want to share your movies online.
If you want to shoot home movies and share them online with friends and family or if you are an aspiring vlogger, you want to be thinking about 30 frames-per-second progressive scan. Even if you are an indie filmmaker drawn to 24p prosumer cameras -- if you've also had a desire to publish your film online, then there are compelling reasons to consider 30p.
I'll go so far as to say that if given the choice between a HD 30i and a standard def 30p camera, I'd get the 30p. Sadly, no such choice exists for under $6000.
So why is 30p more important than HD?