but of course you're now at the mercy of latency time to google's or OpenDNS' nameservers
Nonsense.
Due to the magic of anycast, Google, OpenDNS and others can deploy multiple resolvers around the world with the same IP address and you will automatically be directed towards the nearest one.
That said, because of the way the internet works, you
SHOULD really be using your own ISPs DNS resolvers. Especially if you regularly access content (streams, file downloads etc.) stored on the CDNs. Because the
ONLY way you will be
guaranteed to access the CDN cluster most appropriate for your connection is to use your own ISPs DNS resolvers.
The third-party services may, occasionally, direct you to the same cluster... but I can very much assure you that's by luck rather than good judgement ! It will never be as reliable and consistent as using your ISPs own DNS resolvers. That's a fact, please don't waste your time trying to argue otherwise.
If you use a third-party DNS service (e.g. Google, OpenDNS) whilst attempting to access content on a CDN you will most likely not be routed towards the most appropriate CDN cluster for your connection.
(Well, you could also run your own DNS resolver on your internet connection, but for most people its not worth the hassle and if you're only running a single-homed internet connection, like 100% of home internet users are, you're not gaining anything by doing so either).
Just to demonstrate my point.....
(a) Not using ISP DNS servers I get bounced over to the Netherlands and a total of 13 hops.....
$ traceroute client.akamai.com
traceroute to e1217.d.akamaiedge.net (23.74.104.24), 64 hops max, 52 byte packets
.
.
.
.
7 te0-2-1-0.gr10.saams.nl.easynet.net (87.86.77.163) 39.258 ms 42.035 ms 41.008 ms
8 eth15-2.r1.ams2.nl.atrato.net (80.249.208.229) 40.126 ms 36.600 ms 43.217 ms
9 eth1-1.core1.ams2.nl.as5580.net (78.152.44.77) 38.152 ms 40.056 ms 37.324 ms
10 eth7-1.core1.lon1.uk.as5580.net (78.152.44.238) 44.976 ms 43.875 ms 45.114 ms
11 eth1-3.r1.lon1.uk.as5580.net (78.152.44.101) 44.134 ms 55.931 ms 53.162 ms
12 akamai-20940-gw.lon01-1.uk.as5580.net (78.152.39.70) 43.099 ms 37.794 ms 36.219 ms
13 a23-74-104-24.deploy.static.akamaitechnologies.com (23.74.104.24) 37.190 ms 35.668 ms 37.188 ms
(b) Using ISP DNS servers, total of 8 hops and remain in the UK ...
$ traceroute client.akamai.com
traceroute to e1217.d.akamaiedge.net (2.17.248.158), 64 hops max, 52 byte packets
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.
.
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6 pc5-111.gr10.telon.uk.easynet.net (87.86.69.128) 33.297 ms 32.790 ms 32.147 ms
7 ae2-98.lon10.ip4.gtt.net (77.67.74.109) 29.165 ms 30.029 ms 31.398 ms
8 * 2.17.248.158 (2.17.248.158) 31.109 ms 29.496 ms
Extract from presentation from Akamai to ISPs if you don't believe me (by "local name server" they mean the ISPs DNS server, and by "mapping", they mean internet "mapping", not geographic although in some scenarios the two may be related) ....
