Why should the presence of shebang (#!) freak out ANY security conscious guy?

[Security Conscious <securityconsciousguy () gmail com>]

Could someone please have a look at these twitter posts:

http://twitter.com/#!/achitnis/status/40444144992260096

http://twitter.com/#!/achitnis/status/40447225658228736

http://twitter.com/#!/achitnis/status/40450742326140928

and explain why the presence of #! in URLs would freak out ANY security
conscious guy?

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