Not well known, underestimated, serious potential
A good Demand Side Platform is able to serve ads based on the actual language that is present (-or active) on a specific phone. This creates an abundance of possibilities.
Many clients/advertisers have audiences that have a specific language installed. Think about tourists, immigrants or expats. Companies and government in Amsterdam can target Chinese tourists; for example for a boat tour or safety instructions.
Telecom providers that offer cheap international calling can target their audience in unprecedented ways. Governments are able to reach immigrants with whatever message they desire to serve. Having vast amounts of (global) inventory is - also in this situation – a must.