Multiple phone numbers

Since Nawras started their service in Oman, allot of people tend to have to mobiles for OmanMobile and Nawras, I thought they are mad, but what will people do now? Have 6 mobiles for 6 sim cards or 3 mobiles with dual sim cards?

While I visited Tanzania ( Tz ), which has 4 mobile operating services, ZanTel ( part of Etisalat ); Zain; Tigo; and Vodacom ( part of Vodafone ); people tend to have 2 phones numbers.

One of my relative has one phone and 3 numbers, I end up trying to call each numbere trile & error until I hear the ring tone.