I don't think a $30 billion valuation would be sustainable for Twitter, just like a $75 billion to $100 billion valuation for Facebook wasn't sustainable in the end. So, whether it's a good investment or not will depend on how frothy the markets are at the time Twitter goes out. However, in the long term I continue to think Twitter is going to be a fabulous and extremely important player in media for years to come. Its IPO will be a new chapter in that story. At the time of publication the author had no position in any of the stocks mentioned.Follow @ericjacksonThis article was written by an independent contributor, separate from TheStreet's regular news coverage.