I've maintained for awhile now that the distinction isn't between "big" and "small" data, but between coarse and fine data. Now that everything is done through the web, previously common data sources (surveys, sales summaries, etc) are being supplanted by microdata (web logs, click logs, etc). It does take a different skill set to analyze noisy, machine-generated data than to analyze clean, survey-like data; it's a skill set that is more biased towards computational knowledge than classical experimental design, hence the shift in emphasis.