Hey i'm doing the hsc this year, so i already did my pip. the internet idea sounds really good. you would have to narrow it down from "you can do anything" though. there will be just too much to work otherwise if you don't narrow it down - don't forget you only have 5000 words for your central material. for the internet idea you could say how the internet now contributes to the socialisation process, how the internet is changing social interaction, how the internet have changed things like romance and relationships. there sounds like a really good pip in that topic area though. don't stress about not having a topic yet though. i went through about 6 different topics and i didn't get my final topic until the end of march - so don't worry if you don't know what you are going to do yet.
hope thats of some minor help, let me know if i can help anymore