Call it the opposite of a Valentine.

On the day of love, a web designer named Frank Jonen used the site he was hired to design for a client -- a chain of gyms in California that operate under the banner FitnessSF -- and replaced it with a message informing the world he'd not been paid for his work.

It started with Mr. Jonen yesterday hinting at his plans to his more than 1,500 followers on Twitter. He tweeted: "I bet these bastards still think I won't fight back and let them get away with betraying me and escaping payment. But first, coffee."

That was followed up with another tweet guiding followers to his completed effort, the hijacking of his client's website, where he directed followers. "They thought paying invoices was 'optional'. They ignored all reminders. Let's see if they'll ignore this: http://fitnesssf.com/"

URLs for local sites for gym locations, including one in Oakland, and ones for neighborhoods in San Francisco, including one in the Castro and one in SOMA, in the heart of tech community, also redirected to this message. The contact pages were broken links. Ad Age reached a rep by calling one of the locations who said the claims about nonpayment were not true.

"It got hacked," said one worker who answered the phone at the SOMA gym. "We are trying to fix it now." Said a manager who was handed the phone at that location: "The allegations are not true."

A report about the takeover of the site originally appeared on the Denver Egotist.

Mr. Jonen wrote the following on the site -- urging for anyone who saw his message to take to social networks to protest his nonpayment. (As of the posting of this story, nobody had anything nasty to say to the gym chain on Facebook).

Normally there is no question of paying one's dues. It is simply a matter of morals. Having morals and acting upon them or not having any and just betraying the people that got you started. Sadly we've come to know what Fitness SF stands for, or you wouldn't be reading this.

Your word on their Facebook accounts will go a long way. We're a small company in the heart of Europe, which is probably why Fitness SF believes they can sit this out till we perish. Can you support a company that acts like this?

...I am also writing this on the behalf of the tens of thousands of freelancers and small businesses out there facing larger corporations who can afford to starve them out. In the movie / visual effects business this is already prevalent. Large studios awarding work to smaller studios or freelancers in the hope they won't stand up to them when it comes to loads and loads of unpaid work.

What Fitness SF is trying here is exactly the same ploy. Give a barren advance, rake up a huge bill and ignore every invoice. Rush fees, heavy overtime and weekend work are expected to be free.

You don't get to sleep for days on end, but you do get to wait on your money forever.

It's people like this who cause company after company to go bankrupt.

An injury to one is an injury to all of us. We need to make a stand against crooks like this. If you'd like to join us in this fight, cancel your gym memberships, post on their Facebook pages, Tweet about it or even pass this on to a journalist.