What are some alternatives?
Ambassador - Referral Automation, Made Simple.
OpenX - Ad technology platform available as a hosted service or as an open source download.
TapMango - The most comprehensive & feature rich loyalty program on the market. Keep your customers coming back with a rewards program fully branded to your business
AdRoll - AdRoll is a leader in retargeting display advertising. Draw the right people with the right strategies.
Yotpo - Yotpo is the smartest way to generate customer content, drive traffic and increase conversions.
Epom Ad Server - An ad serving solution for publishers, advertisers, ad and affiliate networks