As a result, any use of these trends has to go through the process of matching up the data to equivalent survey data before it can be used validly.
But what if we didn't have to do all that?
One of the reasons I suspect the Google Trends sometimes don't match up as well as we would hope is that it counts searches not people. A handful of furiously searching journalists and politicos can drive the trend as much as widespread searching across the population. This means that issues may be ignored by 99% of the population but still result in a lot of Google searching.
So the graph above tracks what percentage of all searches in the United States were for the term "Syria" on different dates (these percentages are then scaled to a 1 to 100 index so we don't know the actual percentages).
It's not hard for Google to identify different people either. While there are some complexities to tracking an individual over time, Google has been building profiles on its users for a long time and even a measure of the number of unique IPs that searched for a term would go a long way towards solving this problem.
Having both of these settings as an option would give much greater insight into the breadth and depth of opinion on an issue.
It might even make offhand references to Google Trends as a proxy for public opinion a little more accurate.
Note: There are other reasons why Google Trends data might not match up to public opinion (see the papers) but this is certainly one major concern.