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In all likelihood you have not been penalized. Google does not arbitrarily penalize web site for no reason and as such, unless you can definitively say you have done something wrong then you are ok.
If for example: you linked to a penalized site/page google would interpret your link as a vote for someone that has done something wrong thus passing on the penalty to you.
If for example: your site is new and Google refresh bot took a run by you would be listed by your listing is current not in the primary index yet therefore backlinks would not show.
I suspect that you have not been penalized and a little patience will usually show this.
Sometimes sites can get away with near anything and others can't.
Therefor very difficult to say.
The number of other unique links will though play an important part.
...or you can look at it this way... the less influence any particular change/addon has on the whole, the less potential there is for google to detect to it, and penalize it.
Also have Google showed backword links to your site before, try using alltheweb.com and see if they have found any incomming links to your site, and how long has it been up?