DXL - 1:24 pm on Aug 21, 2013 (gmt 0)
I'm under the impression that the description tag still has no bearing on how a page ranks in Google's SERPs. So no matter what's in your description tag, it really shouldn't influence how that page ranks.
Is not the same but I relate it with an email subject for example. I'm pretty sure many spam filters use that kind of words, is not like putting "viagra" but maybe triggers an alarm.
You're assuming that Google's algorithm functions along the same lines as an email spam filter, but it doesn't. Google does have a SafeSearch feature to filter out adult content, but I don't think there's evidence to suggest that specific words in a description tag will keep you from ranking well.
Whether someone is searching for Viagra, pornography, or replica Louis Vuitton purses Google will still provide relevant results. Furthermore, Google can't recognize the context in which the word "free" appears. It can be in the description tag of a site for a lawyer offering a free consultation, the Wikipedia page for the movie Free Willy, a site promoting a free newsletter or free apps. Not to mention a description tag could have two totally different uses of what can be construed as a negative search. Animal torture: "Visit our site for animal torture videos" vs "Visit our site to end animal torture at commercial chicken farms."