In a recent posting in Google's Picasa forum, someone identified as Google Employee said they are looking at storing facial recognition in image tags. What this might mean isn't stated -- the names identified in the photos, or an ID that then can lookup the names in a database, or what? Also, there's no statement about "when" or even commitment to do so.
The comment was in response to questions about how to backup Picasa facial data, and especially how to share it among home PCs. What MC does so smoothly via its built-in Library Server doesn't exist at all in Picasa.
The other reason to store data/tags in the image files was to allow sending pictures to family/friends and having them see the people names because it was in embedded tags. This is totally lacking in Picasa's automatic behavior, but can be forced in a bit by manually tagging in Picasa. Of coruse, this is also only partially available in MC because it reads but does not update certain "standard" tags.
The whole thing is a huge mess due to lack of true STANDARDS to comprehensively tag images. Therefore, whatever product is used to do all the tagging labor might be the only product that then CAN be used to retrieve the tags. Scary...
BTW, Google stores facial/person data in two chunks. An .ini file in the folder with the picture has data about its face content, and IDs of names that have been matched. The names themselves are in Picasa's proprietary database on the PC used for the tagging. Nothing is put in the picture file. So, once images are processed by Picasa for facial recognition, it might be dangerous to further manipulate them using MC or anything else. For instance, if an image file is renamed and/or moved, Picasa's .ini for that image will become orphaned and the work of identifying faces in it will be lost. Image this happening to many, many image files and the risk is huge.
The only workaround, and perhaps the only safe use of Picasa, is the trick of having it recognize faces and putting them in person albums. Then do manual tagging to put the person names into the image files, then disregarding Picasa's .ini and database system.
OPPORTUNITY? Assuming it's out of JR's field to build a facial recognition system, perhaps it could be feasible to build an MC plug-in that could process Picasa data, import it into MC, then also store it in image file tags -- the crucial pieces Google left out. This would require reverse-engineering Google's Picasa database and .ini file content, but if possible it could make MC a must-have companion to Picasa for everyone who realizes how fragile and limited Google's system is.