Stem cells, for those who are unfamiliar with the term, are a special type of human cell found in bone marrow, fat and other locations, that have the unique ability to develop into pretty much any other more specialized type of cell, given the right circumstances. As such, their potential uses for repair, regeneration and restoration are potentially huge. Scientifically speaking, our understanding of how to best harvest and properly use these adult stem cells is extremely preliminary. But as the saying goes, "never let the facts get in the way of a good story", and that phrase certainly applies here, with the "stem cell facelift".
The LA Times did a properly skeptical review of stem cell facelifts here. Essentially, this procedure has an old name: fat grafting to the face. Of course, that doesn't sound as sexy as "stem-cell facelift", does it? Especially when traditional fat grafting has been a bit disappointing for many surgeons - with short duration, lumpiness, and unpredictability.
Some (but not all) physicians who promote the stem cell facelift are working on enhancing and "turbo-charging" the fat to be grafted by adding additional stem cells to the fat. These cells can be obtained through one of two main sources: liberating them from liposuction-ed tissue with collagenase, as is done with Cytori Therapeutics' $100K+ machine, or separating them from blood, using a process known as apheresis. Adding the stem cells to the fat does seem to make the fat transfer process work more reliably. There's decent science on that part.
But so far, we have no evidence - zip, zilch, nada - that there is any actual regenerative effect on skin when the turbo-charged fat is added to the face. We know you get more volume in the treated areas, so the treatment could be useful for those with a volume-depleted area, or those who want fuller cheeks - but that's about it.
Furthermore, under FDA rules, when stem cells get involved with fat transfers, the procedure falls under a whole new set of regulations. The fat and stem cell combo is now seen as a "biologic agent" by the FDA, and regulated as a drug. In the eyes of the FDA, stem cells and fat represent a non-approved drug. Investigational, yes - approved, no.
Interestingly, one of the spin-offs of this change to drug status is a change in whether physicians can advertise this process. They are no longer just advertising a procedure (the stem cell facelift), but they are doing direct-to-consumer marketing for a drug (the fat and stem-cell mixture) which has not yet been cleared by the FDA. And it's illegal to promote non-approved drugs.
So, those websites you are seeing for stem-cell facelifts are advertising a procedure which is:
1) scientifically not yet proven to have any efficacy,
2) morally questionable, (since they are charging big bucks for an as-yet unproven procedure),
3) illegal under Federal statute.
So there are a few problems to be worked out, eh? That being said, this is an area of great research interest, which one day might really be something good. Stem cell facelifts, for now though, should be part of research studies, not commercial promotion.