To run ads with Skype there are now four ways:
1. Run through retargeting services such as Criteo, Adroll, Adnxs (and many others).
2. Run through some DSP services. In theory, DSPs can also run ads for Skype if they have a service connection. Microsoft opens inventory on AdX for DSP buys. If any DSP has a connection with Microsoft AdX (MAX) it can be purchased, and inventory can be purchased on MSN, Skype, Outlook. Bid prices as purchased on AdX normally. Maybe the future will be. The benefits and disadvantages are similar to retargeting services.
3. It is now known that Ureka, Moore and MicroAd offer this service (purchased via parent company in Japan and resold). Should also be an option.
4. Contact us directly with Microsoft (http://advertising.microsoft.com/en/skype).