Sharepoint global audience does not contain members

Question

I am using FBA for my Sharepoint 2007 publishing site. I write code to add user profile for FBA users (providername:username) and create custom properties. Then at SSP I create a new global audience with property-based rules to target my users. After compiling the audience, I found no member in the audience.

I do not use AD at all and never do a full profile import using the AD connectors. I do not know whether this matters. Where should I start to find out why users are not added in the audience?