First, it’s getting people to use Google to search on these trends compared to the standard of http://search.twitter.com/ or something more specific to hashtags like http://hashtags.org/ (I hear they are having an awesome revamp here in the near future) that will give you a ton more data.

The clients people use support these other methods and not looking on google. And unless google started to do more with this data (and maybe after seeing the other offerings out there they will gank ideas) but again, a major company isn’t going to say “Hey use our Twitter Hashtag and look at it on google.”

Next up on the issues, if you search #seo, it’s 10th on the first page. Unless google starts making this always number 1 then again it’s not going to be a valid tool for watching hashtags. People will go to the tools they are already using for twitter and the more appropriate places.

Lastly, who knows if you will even be seen. First people have to use it and you have to hope they even get to wherever it is on the page, but when they get it that your tweet is even up there and not already moved on.

Longtails won’t work as well because people will be going for specific hashtags and not kind of random things like search. People won’t add words on like cheap and such when they have a specific one they are looking for.

There is just a lot right now that points to there not being a huge value in this right now without changes in how Google handles them and giving a person to even to think to go to Google for that opposed to what is default in their twitter client of choice.