Why now? It's the middle of summer and most Americans are taking vacations - more focused on beach and barbeque than politics.
I think Labor Day weekend will be a perfect time for the announcement. By then, we'll be sick of hearing about the other candidates and a Palin candidacy will rejuvenate the race and get people paying attention again.
That would be true if there was no interent, no talk radio, and no Fox.
She would receive instant recognition as a candidate because her “Q” rating is positively enormous.