edit: thank you downvoters for illustrating the bias on HN. A fake stats piece promoting google as #1 on the frontpage? This place is turning into /. but with more google employees. I'm out.
The reason this is relevant in the discussion is that when you type in the url in chrome (arguably the top browser) the word in the domain and subdomain count as search words that show up in trends. So when you type "plus" for the g+ url it's added to trends. You can check that little fact by looking at the trends for "plus".
If you've already been on Plus, and you're in chrome or (I think) Firefox, it won't do a search when you type "plus" as the top autocomplete suggestion will be "http://plus.google.com. To search, you'd have to key down the list of suggestions.
you obviously aren't familiar with how google trends works. The y-axis is "based on the average worldwide traffic of <search term> in all years". If you search for multiple terms, the y axis is the average of the first term. So to make a comparison, you should have included both terms:
http://www.google.com/trends/?q=google+plus,+reddit
If that were the case, Mitt Romney should start a social network because he's crushing Facebook: http://www.google.com/trends/viz?q=romney&graph=weekly_i...