Welcome to nominative use! <a href="http://en.wikipedia.org/wiki/Nominative_use" rel="nofollow">http://en.wikipedia.org/wiki/Nominative_use</a><p><i>Nominative use, also "nominative fair use", is a legal doctrine that provides an affirmative defense to trademark infringement as enunciated by the United States Ninth Circuit,[1] by which a person may use the trademark of another as a reference to describe the other product, or to compare it to their own.</i><p>Bear in mind that this is a <i>defense</i> and not an immediate get-out-of-court-free card. This fair use exists because otherwise it'd be impossible to refer to trademarked items at all without infringing in some way. After all, you just used the word "airbnb" in your post ;-)
Not a direct answer to your question, but hopefully more helpful in the long run.<p>Focus on the important things. This being copyright infringement (I doubt it is) isn't important. If it got to the point where it mattered, you're very successful, and you can likely change it quickly at that point.<p>Non-competing companies, you should find, are more than willing to help other companies, rather than try to destroy you because of small details like this.
If you say it and the company in question complains, then stop saying it (in that situation the legality doesn't matter as it is a case of BIG v small), otherwise as long as you are not the "airbnb" of a market that airbnb might be in (or want to be in) then you are probably okay... maybe... don't ask a lawyer though, they tend to freak at this sort of thing.
No, what you're thinking of is trademark infringement. As long as you don't claim to <i>be</i> airbnb, or try to make people thing you are in some way associated (or look like you are), you're good.