it's not like it's a journal entry and they are responding to that subject or anything, you know? (unless it's a random "i miss you" comment to the entry!) on those networking sites, it's just comments... comments that you can email, IM, text, CALL or ask them in person later about it. i guess it's like another form of PDA???? let the whole world see how much you appreciate that cake they baked for you and/or how much you miss and love them.
it means more on the internet. lol!