The fact that SlutWalk has rapidly ballooned into a multinational protest movement from an ill-spoken comment by a Toronto policeman represents a distinct and poignant feeling latent in our societies. Namely, the idea that provocative dressing or actions from women in no way holds them responsible for sexual violence.
While the precipitating comment and general thrust of SlutWalk is ostensibly about rape and sexual violence, there is a wider societal issue that is both important and explains part of the broad appeal of the movement. It is the broader idea of sexually suggestive and promiscuous behavior in women - that is, being a "slut" - being acceptable and perhaps even normative behavior.
The pervasive, but rarely articulated, sentiment is that women engaging in sexually suggestive or promiscuous behavior is in itself a bad thing. A women who actively wants sex, who dresses and behaves in such a way to attract sexual partners, and who has casual and frequent sex are perceived to be negative things and that negative perception is labeled as 'slut'. Of course, one can dress provocatively out of far more than just attempting to attract partners - perhaps one is just matching a social custom, for instance - but that often gets the slut label too. What SlutWalk has capitalized on is the sentiment that all of this - that fitting the standard use of the word slut - is entirely an okay thing to be.
There is tremendous power in words which can shape the consciousness and perceptions of society. Words can be used with negative connotations to diminish a certain group of people. Taking back those words and owning them for oneself has been a defining aspect of many great social movements from the N word in the black rights movements, the word class in labor movements, the (to some extent) word bitch in feminist movements, and many other examples. When the actual words change their meaning it symbolizes the underlining changes in social perceptions.
It is thus perhaps the most significant accomplishment of SlutWalk to take back the word 'slut' and transform it from its typical negative connotation to one of an acceptable social behavior. When we get to the point of being accepting of the word slut we are implicitly condoning all of the underlining actions as being acceptable.
That this is even an issue and that people feel the need to express such a sentiment is testament to the fact that the feminist movement has not yet accomplished the equality in social perceptions. For instance, it remains a far more common perception that it is both normal and normative for men to actively want sex and seek to obtain it. Yet for women this has a more negative, aberrant association to it. This asymmetry is, and should be, combatted by SlutWalk. This asymmetry is, incidentally, also belittling of men which paints men in a Hollywood style of drooling over the pretty girl and going to any and all Herculean feats to satisfy these urges. These kinds of defined societal gender roles for both men and women can only have a negative effect on society.
There has been some reasonable criticism of SlutWalk. The biggest issue is that is addresses only a narrow swath of feminist issues and tries to take on only one specific female stereotype: the slut. It is worth establishing that this one stereotype is an acceptable and should not be a negative stereotype. However, a broader feminism movement that is celebrating women of all sorts of diversity and addressing a wider swath of feminist issues is sorely absent. Poor, older, women of colour, women of conservatively dressing religions, and many other identifiers that don't typically fit our media induced standards of sexyness are somewhat left out. Even on the rape issue, most societal factors that increases rape are not being talked about. So there is a bit of an inclusiveness problem. The danger is that because this movement is so wildly popular compared to so many other feminist movements and issues today that it is seen as representative and is too skewed and narrow to be so.
That said, if this is considered merely a part of a larger and more all encompassing feminism movement then it is a good thing to work on advancing this narrow part. Normalizing behavior that might fall into the category of "slut" as entirely acceptable should happen just as it should with many other female behaviors. For that goal, SlutWalk does an excellent job.