Celebrities definitely don't read that much about themselves online- for one thing the sheer volume would make it pretty difficult for them to do anything else with their lives and it's also generally a place of extreme negativity.
Those two worlds collide in the Jimmy Kimmel segment Celebrities Read Mean Tweets which is pretty genius and now in its 10th video. Check it out below.
It's pretty rough stuff, though some folks seem to get a giggle about how mean people are. Russell Crowe is probably going to hunt down that person sharpish and Kiefer Sutherland has a perfect send off.
Can't we just all be nice? Because sometimes a really famous person might see what you wrote.