I stopped actively participating on Facebook a long time ago, and more recently Twitter, too. But I kept the accounts, "just in case."
A few days ago I finally deleted my Facebook account, and today I deleted my Twitter account! ? Merry xmas to me!
I'm aware that it will do nothing to make them forget all the data I've already regrettably given them, nor will it make them stop building a profile on me, but it will at least be one fewer user for them to report to their real customers (marketeers.)