To think that facebook, twitter, and youtube are the only Great Firewall issues is naive. The first two I don't use and the latter only occasionally, and I could live without if necessary. If it were that simple, it wouldn't be too much of an issue to grown adults.

Actually, there are plenty of sites I can't access in China, and also plenty of sites whose home page can be accessed, but not pages that have "naughty" things on them. See what happens when cnn.com or bbc.co.uk run a story on the Dalai Lama, or major riots in China. It might take a few hours or a day or so, but the block will come up. Quite a number of sites run by expats (or ex-expats) about China having to do with media, economics, social observations, domestic political speculations, etc and which can pass on quite useful information (often critical of the Chinese govt) are banned. This is of more importance if you live in China full-time. Without the VPN, I run into multiple sites on a daily basis that are blocked or have certain pages/functions blocked by the GFW. Google something controversial like "Tiananmen 1989 massacre" and you'll not only get a block of the search, but also may get locked out of the Google site for a period of time.

My previous company in China (based in the USA) had its website blocked simply because its IP number was nearly identical to a couple of IP's for pornography sites. The Chinese simply blocked a range of IP numbers, one of which happened to be ours. (We ended up creating a new site hosted in China for China-based clients to access--the point being it was an unnecessary exercise caused by Chinese gov't.)

Excluding the big well-known social media sites, you also have to remember that different ISP's around China don't all filter identically for a given site. This is why people in some areas/cities can sometimes access sites that people elsewhere cannot. ISP's serving Beijing residents tend to be more conservatively set.

On the opposite tack, I have been shut out of websites I need to access and interact with in the USA--such as banking, and certain professional forums--because they (the US sites) have blanket-blocked incomings from Chinese ISP's due to hacking and attacks. I've communicated with the IT departments of some of these sites and it is confirmed. I will not list which because it reveals personal information about myself I don't think is anybody's business. On VPN set to a server in the USA, no problems accessing.

Monitoring of conversations on Skype Tom can and does take place. This includes the ability to pick up "forbidden" words and terminate the connection if the Nannies wish. Or, more commonly, flag the person/traceback on the Chinese end for additional scrutiny. If that doesn't bother you, feel free to use the Tom version while in China.

I happen to be very cautious about these things in China. A few years ago, I got careless with some searching and some talking, and my entire access to Internet from my home was blocked for a couple of weeks. No joke. Phone/internet company could only tell me they were not the source of the problem, and nobody else in the building had issues. Building management went strangely silent and unhelpful. It was targeted, make no mistake about it. Lesson learned.