Forum Moderators: buckworks
It used to be that spiders could hang on queries embedded in url strings with lots of?=$ etc. Thats not the case much anymore, however, a good coder will write clean strings anyway.
I'd have to say that if your looking for a platform for an ecom store then I'd go for Interchange from the icdevgroup. There's too many SE friendly features to list here. And I think you'll find them listed in other threads. Sticky me if you want some examples.
OS Commerce has done a lot of work on this topic in recent years and I think is now OK.
Actinic has a reputation for being very search engine friendly. There's a link on the front page of the .co.uk page to a white paper entitled "Search engines love Actinic". I must declare that I'm self interested here.
Chris