Facebook users have always had a love-hate relationship with the site. It’s creepy, it’s a waste of time, there are too many redesigns, it isn’t as functional as it should be…and yet it is completely absorbing. Five hundred million users can’t be wrong, can they?

But people will get fed up with Facebook — and not because of privacy concerns. We are all talk when it comes to those issues. Every new feature of the web makes our lives more public, and we eat it up.

No, I think the downfall of Facebook will be the marketers’ fault.

MySpace lost its crown when it became overrun with perverts and spammers. I fear Facebook could become a wasteland of fan-hungry community managers looking for Likes. (Especially because I, myself, am an agency-employed community manager.)

The problem is Facebook’s changes have increasingly been catering to businesses rather than average users. There’s the recent wording change from “Become a fan” to “Like,” which helps brands rapidly build their social profiles. Then last week Facebook reorganized users’ profile information so that activities, interests and favorites are linked to corresponding community pages. Any bio information without a natural brand or group affiliation was lost. At the same time, by including a television show or anything else to their favorites, users were automatically registered to receive updates from the related page. That means if I want to make a personal statement about myself by saying I watch Top Chef, I have to put up with Bravo’s marketing messages in my news feed.

I can’t imagine Facebook is putting equal effort into developing ideas to enhance the user experience. Why not improve the system for finding old photos and posts? How about a feature to see all interactions with a friend? Or the ability to see more degrees of separation? An option to forward messages?

These things would make Facebook easier for friends to connect and share with each other, which is what brought people to the site originally. What happens when Facebook is completely optimized for companies to socially network with consumers and lacking in peer-to-peer experience?

People will find somewhere else to go.

Consumers will always look for ways to tune out advertising. That’s why we have TiVo and pop-up blockers. I worry marketers who don’t understand Facebook will ruin the platform for everyone else. As a Facebook member since the time “the” was part of the URL, I am more mindful of how I function on behalf of brands on the site. Facebook is a social space, and marketers are just crashing the party unless they create content people will want in their news feeds.

Facebook might be making it easier for marketers to be lazy, but if people feel bombarded by dispassionate brand messages, they will move on to a new, yet-to-be-exploited option. And marketers will once again be scrambling to catch up.