lucy24 - 9:44 pm on Aug 8, 2012 (gmt 0)

They consider all parameters unless you have explicitly told them in WMT not to. They go by name of parameter, so there's no real difference between the initial ? and subsequent &

If it's "for tracking purposes" or anything similar like a sessionID, it is a very very good idea to tell search engines to ignore it. Otherwise you get the dreaded Duplicate Content-- euphemism for multimultimultiple pages with identical content.