Hello CC...
Well perhaps so, but based on real experience and that of many others (such as at
www.searchengineforums.com) the spiders may be able to handle ?$ dynamic URLs but they sure don't seem willing to crawl and index them.
For example, Lycos states that they will not index any dynamic content (ex: with a ? in the URL)... Altavista indexes dynamic content, but only that which is submitted on an individual basis... IOW, Scooter won't crawl the forums)..
I have read about relatively complex URL rewriting schemes, in particular 404 custom redirects and the like, to gain the confidence of SE 'bots... but it just seems like a long slow journey to getting all our great UBB content indexed and searchable.