If you’re in a hurry to get an answer to this question, the short answer is, probably not. Spamming a competitor’s site will annoy the crap out of them unless they have an automatic spam detection system, but in most cases, it won’t get them penalized. On the other hand, depending on how bright (or really how dumb) your competitors are, deliberately spamming them could hurt them and could possibly penalize them in the Google rankings. Here’s what you need to know.
Spamming, Not Google Bowling
I’ve written in the past about the phenomenon of Google Bowling. This concept basically involves setting up tens of thousands of junk links to your competitor’s site in an effort to get them penalized by Google. Google doesn’t officially say what they do about this.
The official policy is to simply say that Google is aware of it and if they detect something that looks like Google Bowling, they have ways of trying to determine whether it was done by you (in which case you are violating Google’s webmaster rules) or by a competitor. In practice however, the general consensus is that Google Bowling won’t hurt a competitor because Google’s engineers have discounted this already.
However, the point I wanted to make is that here, we’re talking about spamming a competitor’s website. This generally means using any kind of commenting system they have to post thousands of spam comments on their website.
It Could Affect Sales
One place that you definitely may be able to have an effect is by affecting sales of products that your competitor sells. People do this by posting fake reviews on various websites about their competitors and making the claim that their products are inferior. Amazon in particular has been plagued by this and has taken steps to try to weed out spam reviews, both good and bad.
Spamming on the Comments Section
However, if you are trying to get your competitors penalized by spamming them in their comments section, generally this is hard to do unless your competitor is a particularly dim bulb. Basically, there are people who for some bizarre reason I have never been able to fathom set all comments to auto update. This has the effect of creating thousands of comments on their websites, but the comments are all meaningless gibberish.
How it Could Affect Rankings
These spam comments can then affect rankings since Google may assume that a site which has these thousands of junk links on each page is in fact a link farm. This is why it’s never a good idea to allow unlimited comments which have no bearing on what you post. On the other hand, most of us do actively filter spam comments and as such, it’s pretty difficult to use spam to get someone penalized, unless, as I said, they are dumb enough to let you do it.