I know the people/faces feature in Picasa is seductive, but JUST SAY NO! The data is stored in a specialized Picasa database on your hard drive which doesn’t work perfectly in my experience. (Whereas “tags” are stored *in the images themselves* in a standardized way — IPTC — and cannot be lost/mangled!)
It has been my experience (as well as many others — ask Google) that this Picasa-only method (for labelling faces) is flawed in the following ways:
1. Using one shared photo collection amongst many home computers (say on a NAS) is difficult if you rely on special features of Picasa (or iPhoto I assume). Not impossible, but only for extreme power-users. If you ignore most of the fancy features of Picasa and stick with tags, you should be ok.
2. Many people have experienced problems with picasa losing track of their database (and hence all of their face data). I believe there might be ways to “get it back” — again, ask Google — but you really don’t want to go thru this nightmare!
So.. just stick with hitting “Ctrl-T” and adding tags for the people or other labels you’d like to add. Captions are safe too. Those are stored in the image file too! Or if tags scare you too, add the data to the file name!
Yes, I know you will lose the cool feature where you outline the face allowing you to visually see 100s of your kid’s face in a collage, etc. But I bet you will be able to add that back in in some future year pretty easily — the faces tool in Picasa and other photo apps will only get better and better. And you’ll have already tagged many of your photos so you’ll be half way there.
Wanna test it? Add some tags to a photo, then go look at the image file in Windows Explorer or Mac Finder and view properties. Your tags (and/or caption) will be there! Search works great in Windows too (as well as Picasa). Just click “search file contents” and your tagged images come right up! You can even make the tags visible in the results. It’s an optional column in Windows. And you can of course add tags right in Windows. Picasa just makes it easier.
Cool! Simple! And future safe!