According to Business Insider, the issue was the result of a technical hiccup — something which is to be expected given that the social networking service is still in "field trial" mode. Google's Senior Vice President of Engineering, Vic Gundotra, was quick to provide an apology for the troubles as well as a bit of a clarification in — what else? — a Google+ post:
Yes, laugh all you want, but even a service run by search engine giant Google can temporarily run out of disk space if its engineers underestimate just how popular it will become.Don't worry though: Whatever issues there were over the weekend appear to be resolved at this point, so we're assuming that someone at Google pulled a few switches and pushed a few buttons to allocate enough sufficient disk space to Google+ and its eager users.