I just thought it would be interesting to share this bit with readers. Below is a graphic of how many users *added* a certain mashup to their Sampa site on month of December. Notice that it doesn't represent how many users are using a specific type of mashup because users might have added it and remove it later or users might have added before the month of December.
YouTube (42%) is the #1, followed by Flickr (38%) very closely. Then we have Blogger (9%), Delicious (6%) and BlueDot (5%).