Of course, it's not as if the Olympics were previously insulated from political machinations, as the dueling boycotts of the 1980 Moscow and 1984 Los Angeles Games demonstrated. But, Farrell argues, the dynamic of where the pressure is coming from has changed significantly:
The dynamic driving the Beijing Olympics seems to me to be rather different; what we are seeing is that the politics of boycott is being driven by mass-publics, and most recently by protestors, rather than by political leaders. In the absence of the public unrest that has culminated in the recent protests in Paris, I doubt very much that Western political leaders would be muttering about not showing at the opening ceremonies – the geopolitical stakes of market access etc are likely more important to them than the fate of Tibetans. But given the widespread public reaction in the West, even leaders like Gordon Brown, who obviously want very much to attend, are having to insulate themselves from public pressures by taking other actions liable to annoy China (such as meeting with the Dalai Lama). In short, I think we are seeing how public opinion and organized cross-national opposition can create significant constraints on the ability of leaders to respond to what they see as the geostrategic necessity of keeping China happy. This is, as best as I am aware, a new phase in the development of the Olympics.
In other words, the Olympics offer a new avenue for grass-roots public anger to manifest itself in actual pressure on global leaders. This is because the Olympics are a high profile example of international recognition and engagement, and one that (between the presence of hordes of news media, athletes with personal agendas that don't map on to diplomatic niceties, and even the easily protested torch-run) offers a nearly unparalleled opportunity for media-friendly protests.
On the actual merits of boycotting the opening ceremonies itself, see Steve Clemons versus Daniel Drezner.