Awareness expands when you click Like on a Facebook page. Your community automatically sees everything you Like.
But, does Like lose its meaning when a company says "Like and be eligible to win something"? [I guess you can't blame people who Like your offer if they stand to get something in return.]
As a marketer, I refrain from baiting people to Like my article, or product or website, etc. Otherwise, how would I know how many people really Like my product or service or article, etc.?