1) Yes, there are several DNS service providers that offer BGP anycast with geographically aware failover / load balancing. UltraDNS and DYN are the larger ones.
2) Yes, some ISPs do set a minimum TTL. Although BGP anycast is the most effective as the first line, sometimes it makes sense to have your reverse proxy caching layer override that distribution based on GeoIP and redirect to a more suitable proxy node closer to the client. This is especially the case when people using recursive lookup DNS servers that aren't necessarily geographically close to them (e.g. 8.8.8.8). It could also be useful in cases where TTL expiration hasn't caught up yet though.
3) No. Think of BGP Anycast DNS as distribution at a global level, and dedicated load balancers as distribution at the local level. You need to work out how to get the traffic to the load balancer first, and load balancing across distant geographies (high latency) results in horrible performance.
2) Yes, some ISPs do set a minimum TTL. Although BGP anycast is the most effective as the first line, sometimes it makes sense to have your reverse proxy caching layer override that distribution based on GeoIP and redirect to a more suitable proxy node closer to the client. This is especially the case when people using recursive lookup DNS servers that aren't necessarily geographically close to them (e.g. 8.8.8.8). It could also be useful in cases where TTL expiration hasn't caught up yet though.
3) No. Think of BGP Anycast DNS as distribution at a global level, and dedicated load balancers as distribution at the local level. You need to work out how to get the traffic to the load balancer first, and load balancing across distant geographies (high latency) results in horrible performance.