There have always been questions for which Google wasn't the best place. Niche forums, obscure government databases, and even things like HN...I routinely use searchyc.com over Google. Twitter is only slightly more relevant to the wider population than any of these...I sincerely doubt that real-time search will ever be more than 1% of the overall search market. There's just not that much that really matters if it's 30 seconds ago vs. 30 minutes ago.