The face on the cover of Watchman

This is a bit random, but last night I had a dream in which everywhere I went I saw a big yellow smilie face, and the only conclusion I could come to was that it had to do with the cover of the watchman.  What exactly did that face symbolize?  I know that the comedian wore it and that it appeared on a ledge outside on a terrace, but what did it actually mean?  I had the theory that it might be like a face on a clock, but seeing as there is no clock in the smilie face itself, I then jumped to the conclusion that it might have symbolized being watched.  That there is always someone watching you.  I am still not sure what I believe it to mean, but those were just some ideas I had while reading the comic.