Oh, I think that the USPTO would likely take exception with very common words, but, then again, most trademarks are only valid for a segment of the total market. That is, if IBM had the word ``International'' tradmarked, it would probably only be valid in the computing (or business, or whatever) world, while
International Truck and Engine could have it in another, and
Amnesty International might have it in another (to stretch who might be having such a trademark).
You can also get trademarks on specific logos. They refer to those as a ``stylized or special form'' mark, as opposed to the earlier mentioned ``typed'' marks.
And for those of you that were wondering what ``service marks'' are (you can see little ``SM''s on things sometimes where you might expect a ``TM''), they are the same thing as trademarks, but used to represent services instead of goods (meaning physical products).