'Unless it's a large CRM or identity management system, I've found MySQL to be robust and scalable enough,' said Meadows, president of Live Oak Interactive Inc., an Austin-based Web development and hosting firm. And while he acknowledges that 'you can do quite a bit within the parameters' of the express databases, he fears that vendors will pressure him to upgrade to an expensive supported version of their database.

Rajeev Kaula, a professor in Missouri State University's information systems department, said Oracle XE is easier to install than earlier 'lite' Oracle databases and helps teach students to program more efficiently.

'Students who honed their skills on MySQL and PHP tend to treat databases only as a way of storing tables,' Kaula said. Learning on Oracle XE, 'they are realizing the power of transferring the business logic to the database itself.'

Where MySQL proved popular with dot-coms needing to quickly deploy back-end databases, today's Web 2.0 start-ups are creating more complex Web applications, such as AJAX-based Web sites that may benefit from features such as more powerful XML data storage capabilities offered by the commercial databases, said Burton Group's O'Kelly.

And Savvica's Green said that contrary to the perception that Web 2.0 start-ups are wedded exclusively to the LAMP (Linux Apache MySQL and PHP/Python/Perl) application stack, he has gotten a lot of interest from peers who were unaware they could get free versions of SQL Server, Oracle or DB2.