Has anyone tried contacting someone on craigslist for an apartment?

I am trying to do this and they are not responding, two apartments came up in the city I live in, Fremont, which I am very interested in, and I contacted them through craigslist. I doubt there is so much competition for these two apartments. One I contacted within an hour of the posting and the other I contacted the next morning after 10pm it posted, 6am I contacted them. Does anyone have any experience with slow craigslist reponses, or why they would not respond?