In the video setup the image appears with a correct aspect ratio of 1.33. It is in the transmission where it gets distorted.
I believe the 352 x 288 pixel picture is determined by the codec used. I seem to remember NetMeeting used the same resolution and had this same defect.
I believe this is a defect of Messenger and not of the webcam. I believe any webcam with an aspect ratio of 4:3 (which is pretty much all the ones I have ever seen) will have this problem with Live Messenger.
In other words, I believe most people are having this issue but they just don't notice or don't care. I suppose many will prefer appearing more slender
The Common Interchange Format (CIF) Video standards, known as H.261 and H.263, were developed by the International Telecommunications Union.
CIF NTSC resolution: 352 x 240
CIF PAL resolution: 352 x 288
So it seems the video stream is sent with a different aspect ratio and the receiver should stretch or compress horizontally to restore the correct aspect ratio.
http://en.wikipedia.org/wiki/Common_Intermediate_Format
xCIF pixels are not square, instead having a native aspect ratio of ~1.222:1. On older television systems, a pixel aspect ratio of 1.2:1 was the standard for 525-line systems (see CCIR 601). On square-pixel displays (computer screens, many modern televisions) xCIF rasters should be rescaled horizontally by ~109% to 4:3 in order to avoid a "stretched" look: CIF content expanded horizontally by ~109% results in a 4:3 raster of 384 × 288 square pixels.
So it seems the answer is that the Live Messenger receiver should expand the video horizontally but it is not doing it.