Impossible to scale: Google+ API limited to 10,000 requests per day
89n.com
89n.com
TL/DR- 89n requested a limit bump to 1m requests/day but only got 10k/day.
Facebook's open graph seems to have a 100m/day/app limit. (http://www.quora.com/Whats-the-Facebook-Open-Graph-API-rate-...)
So this Google+ quota isn't surprising, coming from Google.
In the early days of audioscrobbler/last.fm, I added comments to the HTML of our pages, asking people who were writing scrapers to get in touch so we can add additional webservices.
It's much cheaper to serve up an API request, and trying to block scraping is futile.