It's just good business sense to read any document carefully before you sign it. But on college applications, a lot of students don't read the fine print in the signature section. They just sign and send.
It's important to understand what you're agreeing to when you sign anything. Here's some of the text from the signature section of the Common Application:
I certify that all information submitted in the admission process-including the application, the personal essay, any supplements, and any other supporting materials–is my own work, factually true, and honestly presented..I understand that I may be subject to a range of possible disciplinary actions, including admission revocation, expulsion, or revocation of course credit, grades, and degree should the information I have certified be false.
Based on this agreement you're signing, if a college were ever to find out that you lied on your application, even a little bit, they could take back your admission. They could kick you out of college. They could invalidate classes that you've taken. And if you've already graduated by the time they find out, they could take away your college degree. No refunds, by the way.
Considering the possible consequences, it should make it easier to answer the question about whether or not it's worth fudging the truth a little bit on your app. I don't think it is.
It also says…
I affirm that I will send an enrollment deposit (or equivalent) to only one institution; sending multiple deposits (or equivalent) may result in the withdrawal of my admission offers from all institutions.
Later this spring when acceptances arrive, a lot of students are going to refuse to make up their minds by the May 1st deadline. They (with their parents' knowledge in most cases) are going to plunk down deposits at multiple schools just to buy a little more time to come to a decision.
But once you sign your Common App, you've verified your understanding that if you place multiple deposits at more than one school, all of the schools that accepted you can withdraw their acceptances. Again, it just doesn't seem like it's worth the risk to me.
Once you sign the document, you can't claim later that you didn't know the rules. Read it–and understand it–before you sign.