I guess that is my point. You are looking to engage with your followers using those terms, you aren’t just posting about your day. You have a reason for looking, you are part of the target market I am referencing.
Many users don’t even use the twitter.com interface. If you use a tool like Tweetdeck or a Twitter App on your smart phone, chances are you NEVER see the trending topics.
I am not saying this decreases the value, I am saying it INCREASES the value because an advertiser has a targeted market. However, it would decrease the value for some advertisers because they don’t sell their product or service to that market.

Now, if you are looking at marketing and staying up on the pulse of what potential customers are discussing, I will look at it as part of a whole research effort. if other end users are like me that would mean that the best target audience for this new paid element are companies that are targeting marketers!