klark0 - 4:37 am on Oct 5, 2012 (gmt 0)
Not using Webmaster Tools puts yourself at a disadvantage - not getting messages/alerts + no keyword data if 'not provided' is a huge chunk of your traffic.
Only reason to not use GA and WMT is if you're trying hide ownership/association between sites or if you're running some kind of SEO network. They don't use GA for rankings or algos. Plus not enough webmasters use it. And you can always opt-out if you don't want your data shared anonymously.