Al Ahram has an article claiming to uncover the "secrets" of the smuggling tunnels between Egypt and Gaza.
According to this report, in June 2008 Hamas and Israel joined in cease fire, and one of the parts of the deal was that if the calm held, Israel would increase the number of items allowed into Gaza.
Although rocket fire decreased, the article claims that the militant groups in Gaza held by the deal. The rockets that were shot were not launched by Hamas or Islamic Jihad - but by the tunnel owners themselves!
The tunnel owners were making millions on their illegal smuggling, and the idea is that if they would shoot rockets to Israel then Israel won't allow as many goods into Gaza, protecting their investment.
This is somewhat possible. While Israel's responses to rocket fire would often include bombing the very tunnels that these traders were supposedly trying to protect, it is true that at the time, there were a number of attacks at the crossings themselves, and Israel would respond by closing them for safety.
Also, clearly the smugglers would have easy access to rockets and mortars.
So while I doubt that the bulk of rocket attacks in the second half of 2008 came from smugglers, I can believe that some of them did.
Al Ahram goes on to discuss how the tunnel trade was hurting Gaza's economy, as ordinary people were investing in tunnel building rather than putting their money somewhere comparatively safer. Some even sold their homes to fully invest in the tunnels in hopes of striking it rich, and many lost everything during Cast Lead or to unsavory tunnel operators who would take their money and then claim that it was all gone.
As always in the Arab media, one must look at why such a story is being published when figuring out how true it is. Al Ahram is following the Egyptian people's pulse in being against Hamas and Gaza, as many Egyptians believe that the smuggling of fuel and goods to Gaza are adding to shortages in Egypt. (This is almost certainly true where there were fuel shortages in the Sinai.) The Egyptian army, the most popular institution in Egypt, has been shutting down hundreds of tunnels in recent weeks.
There is no love lost between Egyptians and the Gaza tunnel owners, and this article is part of the propaganda against Gaza that has been circulating in Egypt since the latest revolution.