Jon,
Venture capitalists sponsor public events just like any other organizations which want to set themselves apart from their competition. E.g., http://etl.stanford.edu/about/
Absolutely. In particular, they like to get their name in front of promising entrepreneurs, as finding interesting companies is essential for their business. So if you pitch them, I'd try to find some reason they can see it as a useful marketing expense.
Alternatively, rather than pitching venture capital funds, it might be worth talking to individual venture capitalists, who are just the sort of person to be fascinated by Wikis. For example, Mitch Kapor and Vinod Khosla are both tech investors and major Wikipedia donors.
William