If they are taking 9 of the top 10 places and using subdomains and other tricks to get multiple results for the same content, then you may wish to report it to Google. Note that this forum is not a way to send messages to Google.
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[webmasterworld.com], though, does describe the best four ways to report the situation, should you wish to go that route. It's also not likely you'll see immediate action. Google tries to find algorithmic solutions, and they also need to prioritize problems based on user demand and urgency.
If the other site isn't using spammy techniques, though, but simply getting multiple listings on the same domain, or is ranking, say, on foreign TLDs, then the situation isn't one I would report. Take a look at these threads to get a sense of what might be happening... Host Crowding vs Brand Authority http://www.webmasterworld.com/google/4464096.htm
Noted in the Brand Authority discussion is another discussion, which brings up a specific site, something we don't generally do, largely because of outing potential. We ask users not to post specifics. The site in this discussion, though, is large enough and widely discussed enough that we did allow it to be identified.... How Google is Showing the Results http://www.webmasterworld.com/google/4381552.htm
I should ask also whether your search might be interpreted as a branded search, for keywords incorporated in your competitors brand. The fact that you're in first place suggests not, but I felt it worth asking.
Also, how long have you been seeing this happen?