This is true when you are an active writer, anyway.
Yes you can --> change your signature.
Once you've changed the signature but you didn't post a new message, but anyone else replied to a thread that you were active sometime ago --> then your signature will be also captured.
And then, searching for expressions used in the signature these are on top of the results!
Now let's talk about the opposite:
a) you don't write articles and
b) nobody is replying to older threads.
In this case this one
![Image](http://lh4.ggpht.com/_99eyu2EDGzc/SYPAi22l4II/AAAAAAAAAG0/uGGCWjU9Ev8/s800/toetensen.jpg)
seems to be arbitrary and is in need of an explanation.
Why pizza? Why pico?