It is not true that you have to combine things as a novel compound word (as with 'craigslist' and many other tech firms) in order to obtain trademark protection. Common names and plain words/phrases can be protected too, within a well-identified field of use, by either formal registration or force-of-use-over-time.

"Craig's List", in the field of an online listings site and community, is just as protectable as the smushed-together version. And, by risk of confusion with 'craigslist', the two-word version is now just as excluded from others' use as if 'craigslist' itself were named "Craig's List".

Even if your name is 'McDonald', you won't be able to open a "McDonald's" hamburger chain. If you wanted to sell cash registers worldwide, you couldn't start an "International Business Machines". You couldn't even get away with "Jonathan's International Business Machines".