Coming back on to this rather old topic. Aerospike now have no issues with depoying across availability zones and, indeed, recommend it.
There are tradeoffs in using multiple AZ vs. single AZ in terms of latency or redundancy. (ie: if an AZ completely goes down in Amazon)
You would have to decide if you want to optimize for read latency, redundancy.
It may help to test for your use case and determine if any of these features will help and decide which trade-off will work for you.
With multiple AZ you have protection against an AZ outage but could have increase in write latency and leverage client rack-awareness and replication-factor for reads.
With single AZ you reduce the risk of latency for write transactions and intra-node network connectivity issues at the risk of AZ outage.