What is MSN [bot]???

...and why do I see it among the names of those cruising the forum every once in a while (but in stealth mode... coloured so it's hard to see)?

Its just a search bot for MSN web search. Google and Yahoo use them along with pretty much any search engine


So, is this where they capture pages for cache or something else?

Yes. Bots are used on forums because they are much more dynamic than other web pages.