There's a good chance that once the zombies rise, or very soon afterward, that many of the forms of communication that we rely on and take for granted will cease to exist.
Infrastructure will be destroyed not just from the zombies, but from panic (raiding/vandalism), decay, fear, etc. Until that happens though, many will just see the threat of zombies as some kind of joke, or the delusion of people that have seen too many horror movies – or need a random and consistent theme for blog posts. It's important then, that once the attacks begin, that anyone "in the know" turn immediately to any available channels of communication and begin organizing friends and family and getting them to do the same.
That last blast of organization and planning could be the thing that ultimately saves humanity.