Actually, this is no longer true. There's plenty of money being spent in the US on Internet TV at premium rates (as high as $60 CPM), but the problem is that all of this is still being bought with an old world mindset. (To be fair, this perhaps isn't surprising considering that traditional TV is still being bought for $20-25).
But, television is still about scale. It's about piling them high. Not about targeting.
So, you might run a very 'successful' Internet TV station with 500,000 unique users a month all interested in 'Subject Y'. Great, but the trouble is this audience is spread over 102 countries, with the highest viewing (85,000 per month) in the US.
Now, the problems being:
1) All ad budgets are national, not global
2) 85,000 is 'far too small' to be considered by a mainstream advertiser in the US (or rather, their media agency, where such tiddlers are a pain in the proverbial monthly reporting spreadsheet).
Such concepts as 'targeting' do not even come into play.
The old world just can't help themselves. But, there again, maybe the answer is an aggregated video service, a kind of long tail Google for the video world... Any ideas, anyone ?