The talk about the increasing popularity of the Muslim Brotherhood among protesters is very true. It is not government propaganda. The politically motivated religious group, which is officially banned by the Egyptian regime, did not participate in the protests from the beginning as a group, but as individual Egyptians. On the second week of revolution, they decided to come to streets with their collective identity as members of the MB group. They did not use any specific MB-related or Islamic slogans, but they moved together in blocs.
Since Friday, the Muslim Brotherhood are dominating the protesting scene, especially in Cairo and Alexandria, although of course, there are so many other protesters from various groups: leftists, secularists, and liberals. Also, on the political level, we have seen them negotiating on behalf of protesters with the Vice-President, which can be interpreted as recognition from the state of their legitimacy.
That was not the case before January 25. That triggers the very important question on how big is the potential for the Muslim Brotherhood to lead the country after Mubarak leaves either now or after the end of his term.