They may or may not be aware of but I know a few who has been doing some of these.
They may get away with it for some time, even a write an ebook on "how to get on page 1 of Google in 10 minutes", etc. But one day they wake up and their website is gone from the SERPs. If that is a business you depend on, you wouldn't want that to happen would you?
Link baiting - while not entirely bad in itself link baiting can hurt your site's standing in the search engines when these links are coming from sites whose content has no relation to the content on your site. Say you are running a scrapbooking website and you had links coming in from weight loss sites, this would not look natural and might alert the search engines.
If this were true what would stop your competition from doing this to you.