Does this apply to folks with personal blogs like Fred Wilson and Mark Suster or just big corporate blogs like TechCrunch and GigaOm?
That applies to any investor or insider, regardless of where they speak publicly. So, it applies to Fred Wilson, Mike Arrington, and any other investor.
Blogs like TechCrunch and GigaOm are more journalistic in nature - their goals and the public's perception of them is as a news source. There are certain responsibilities and standards that need to be upheld when you are a source of news that don't apply to personal blogs.
http://en.wikipedia.org/wiki/Regulation_Fair_Disclosure
For privately held companies there is no equivalent afaik.
Especially critical is the time of transition from a privately held company to a public one (IPO). And that's good stuff. The basic idea is that everybody has access to all the information at the same time.
The big issue would be if a blog or some other communication wrote 'you should buy this stock' knowing it is a lemon and unloading by someone with a hand in the creation of the blog.
That's why it is good practice to fully disclose that you have a position in the companies you write about, because if you do not it may be that afterwards, long after you thought it mattered you could still be hit with a violation depending on what he stock did after you published.