There doesn't seem to be a real definitive answer to this question. back in 2008 Google talks about exploring new and improved ways to crawl pages including some HTML forms. It's been almost 5 years since then so I'm sure they're doing more than before. I would still however include some text links on pages if you're looking to send web crawlers there. Also make sure that you have a solid sitemap to help the crawlers find your content on these pages.
I have never seen it... In the last 10M pages Googlebot has spidered on this site, Googlebot has never done an HTTP POST of any sort (only GET).
^^ same nothingh like that has happened on my site either and it has spidered my site thousands of time.