Apparently the Algerians first noted drone activity in the south in 2004, partly as "facilitators" were not very discreet in transit.

More recently there has been the traffic between the refugee camps around Tindouf, for the Sahrwis (from former Spanish Sahara), where the appeal of their Marxist-Leninist leadership has diminished for some of the younger generation and the appeal of the insurgents / bandits across the Sahel has had an impact.

General background:http://en.wikipedia.org/wiki/Sahrawi_people

As one observer explained there are no border in the Sahel, it is a three day journey in a modern vehicle. Note the Sahrwis are not Tuareg's.