At the risk of increasing thought before posting, it may be best practice to point out that deleting anything one has written upon the internet has absolutely no effect upon the people who may have either copied the post with copy/paste ( or saved the whole page as a file ); nor upon search engines --- I've seen threads from here posted within a few hours of their initial release available on Google.
Theoretically people can request Google to remove items, but a/ it requires adequate reasoning, b/ I doubt it often works, c/ I bet they neither like unprofitable tasks nor wish to spend their time reading lunatics' requests --- which is what would happen if this practice became popular. Besides which, stuff is still stored in Google's cache-banks, accessible to the manically determined; and there are plenty of other search engines busily squirrelling away the Vital Thoughts of the People, whether from Youtube, here or any other site on the net for as near eternity as the internet lasts.
Could be 20 years, could be 200.
Claverhouse
