The company owned by online auction powerhouse eBay marked the occasion with an inaugural PayPal X Innovate conference in San Francisco.

Internet entrepreneurs flocked to the gathering, which continues through Wednesday.

PayPal engineers addressed rapt audiences in sessions and seminars devoted to the mechanics of building secure financial transactions into just about anything linked to the Internet.

"The big claim to fame is we made things very easy if you want to pay for things online," PayPal president Scott Thompson told reporters.

"The Internet is doing things to people's lives today that nobody imagined, replacing longstanding industries. At the end of the day, you want to take advantage of that."

The sold-out conference delivered on Thompson's promise two weeks earlier that "PayPal will be the first global online payment service to open its platform to everyone."

The scene featured curtained meeting rooms, bean bag chairs and even classic arcade games such Asteroids, Tetris, and Pac-Man. Tables were laden with snacks ranging from energy bars to gourmet jelly beans and Twinkies.

Companies that had gotten head starts on building PayPal X services into their websites showed off their creations.

Andrew McPhee and Ebony Charlton traveled to the gathering from London, where they launched technology startup expensure.com as a service to help friends or flat mates divvy up shared expenses.

The Web developers were sharing a flat when they devised the application.

"You can keep track of who owes whom what," McPhee said. "Whether you're traveling together or sharing a flat."

Building PayPal X into expensure.com spares users the "pain" of having to navigate from the Website to take care of money exchanges and lets the service track that payments were made, according to McPhee.

MedPayOnline.com used PayPal's open platform to provide a way for patients to pay doctors, saying the move addresses a need in a multi-trillion-U.S. dollar health care market.

"They are using PayPal X to improve the way consumers pay for medical bills and doctor visits, making the everyday lives of consumers easier," said PayPal platform vice president Osama Bedier.

Storenvy.com used the conference to launch an online social shopping community that connects merchants with shoppers in a social setting.