Um, I don't think we'd say no unless it was insulting or a scam.  Or spyware.  Or warez.  Or virusy.  Or of an "adult" nature (i.e. "to click this link you must be 18", etc.)  But, I guess if you want to put a link to your travel agency in your sig, go for it...but, I'd definitely be subtle.  Subtle works.  A paragraph-sized sigline does not always.

Or, for another answer.....

42. 

/nod

(Yes, feeling goofy.  Sorry)

edited because I apparently don't know how to spell "it"

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