Your second question is really composed of two questions again. Let me answer separately to both.
1) Is lithium able to mesure visitors/returning visitors?
I always try to keep things simple and only do them once. On that principle, I would measure the visitors, visits and returning visitors in your portal's analytics (either Adobe or Google) rather than anywhere else. This will ensure a consistent measurement and will allow you to analyse customer journey across your portal. You want to be able to measure Lithium's effect on conversion rate, increase shopping and increase basket size. You can only do that if you can follow the customer journey across the community and across you whole portal.
2) How many quotes have been given by a single visitor/person?
One way you can look at the "Lithium Community Platform" is as a "conversations repository" in the cloud. We have a set of API for every module or stage of the platform. Every action is attached to a user. So, yes, you can retreive any conversation from any part of the structure of your community related to any specific member of the community. Additionaly, the information of each member's profile can be accessible depending of your configuration settings.
Hope this helps.
