I find scribd's feature set to be useful, and pdf's to be a pain to deal with. While there are times I like to have a file on my system, 99.7% of the time bookmarking a pdf on scribd in delicious is much more user friendly to me.
it should be my choice what i want to do with a pdf. viewing in scribd is one of many things i might want to do. yc shouldn't make that decision for me. scribd should release a browser plugin instead (if they haven't), and leave it up to users
