Analysts put the problem, which affected other major sites including telegraph.co.uk and password manager service LastPass, down to a little-known, but crucial part of the 'nuts and bolts' of the web called the Border Gateway Protocol, or BGP.
BGP is essentially the 'route map' of the web, allowing internet firms and large networks to send information to each other via hundreds of thousands of complex paths.
When surfers visit a website, they rely on machines called routers to keep a table of known, trusted routes through the ever-expanding tangled web.
Now older routers are struggling to cope as smart-phones and tablets allow more people to access the web, more of the time - meaning routers need to be updated to cope with the extra traffic because of a lack of memory and processing power. Some machines impose an arbitrary upper limit of 512,000 different routes, a number that experts say is beginning to look out of date.
This appears to be what brought down eBay, experts have said.
Dr Joss Wright, a research fellow at the Oxford internet Institute, said: "It's really a case of the routers being over-loaded due to more and more devices, and more and more fragmented internet landscape of lots of little networks."
Routers were increasingly unable to cope with the increased traffic, Dr Wright said, in the same way as a human brain would not cope with remembering "all the back streets" on a long journey.
James Gill, chief executive of internet traffic monitoring firm GoSquared, said: "This definitely won't be the last we hear of BGP outages."
The problem is partly to do with computers relying on out-dated IP addresses - the unique code given to each computer - Mr Gill added, with the old, numbers-only system only gradually being replaced by the alpha-numeric IPv6 system which allows more combinations.
"In that sense, it would be right to describe the internet as full because they are running out of IP addresses to go round," he said.
It could cost large firms such as Ebay millions of dollars to upgrade all their hardware. Business analysts said that a repeat of such network problems could cost online retailers and other businesses that rely heavily on the internet, millions of dollars in lost trade.
Richard Perks, from the market analysts Mintel, said: "If such problems become a regular feature, then that is a serious problem both for firms and for the economy in general."
