1st party data

There is a very interesting trend occurring within the Real Time Bidding (RTB) space that deserves to be noted.

Large advertisers with very large 1st party data pools are currently utilizing DSP's to manage their retargeting campaigns. But there is a trend where these large advertisers are starting to go direct to Exchanges in addition to their DSP method. This allows us a few interesting deductions:
* Retargeting campaigns are very successful (ok no rocket science here)
* Large cookie pool owners, want more of that success
* DSP's are hitting a ceiling and somehow are leaving unsold wanted users on the table at the large exchanges

But wait, DSP's are suppose to offer global frequency capping across all exchanges and be a one stop shop. Why then are large cookie pool owners going direct to Exchanges over and above what they are doing with DSP's

Is the DSP algorithm distributing wanted users across multiple advertisers? This isn't a huge deal for a SMB advertiser, but the larger advertisers are saying, hey, we know there are more of our wanted users our there and we will go direct to Exchanges to get them?

I don't have all the answers, but suffice it to say if this is a trend, it will have large implications. I would love to hear any and all opinions on this topic.