I mean besides the universe imploding in on itself because Tik Tok made it's way into fine literature.
Referencing current cultural phenoms is a habit of mine, probably from watching so much television (thanks a lot, P-i-C). Hollywood is so about the "now" that everything becomes five minutes ago. We're such a satisfy-me-now culture that we need to constantly be fed new entertainment. This has fed into our television shows, movies, and celebrity blogs in the form of ripped from the headlines stories. Jokes about Lindsay Lohan's ankle monitor abound (I may or may not have made a joke about that myself yesterday), TV shows like Law and Order televise episodes about the latest political scandal, and Saturday Night Live continues to amaze me by making skits about stuff I've never even heard of.
And all of that is fine for those mediums because they are instant. TV shows get scripted, revised, shot, and aired in a matter of months. Live shows like SNL happen every week. They can afford to reference the here and now, and in fact they have to if they want to stay current. And I'm as big a sucker as anyone else for a good Britney joke.
But literature doesn't work this way. Books can take several years to write, and several more to get published and out into the market. It doesn't matter if you're writing a YA novel, an adult contemporary, or even a graphic novel - keeping your work current means keeping current references out of it. Slang, celebrity references, and memes will date your work. Sometimes this works, like Brett Easton Ellis novels, but sometimes it doesn't. This is especially true in young adult writing, but it happens in all genres. Any references that tie your work to a specific time/place/decade may make it stale for future readers.
Even popular books suffer from this affliction. For instance, I bought How To Win Friends and Influence People by Dale Carnegie a few years ago. A timeless book, right? Well, not exactly. A note was included in the beginning of the book that many references to popular figures were updated for a current reading market. The book was written in the late 1930's and included examples of well-known businessmen of the time that are not so well-known now. They didn't foresee the success of the book at that time, so they didn't think to make it less referential.
So the key to keeping your book "classic" is to avoid timely references to events, unless that's the specific topic of your book. And if that's the case, you can make all the Britney jokes you want. Don't worry, I'll laugh right along with you. If they're funny.