Things that make you say, Hmm

or Holy Social engineering Batman I think the Joker has one on this.

A long read but interesting;
http://www.computerworld.com/s/article/9216484/Elgan_How_to_pop_your_Internet_filter_bubble_?source=CTWNLE_nlt_wsmgnt_2011-05-12&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+computerworld%2Fs%2Ffeed%2Ftopic%2F169+%28Computerworld+Web+2.0+and+Web+Apps+News%29