The problem is precisely that it's too difficult for grassroots volunteer groups to put measures on the ballot, while at the same time being too easy for well-funded private interests to get things on the ballot, which has resulted in the current distorted use of the initiative system.

Most initiative signatures are not collected by volunteers, they're collected by paid signature gathering organizations. And that's the problem the article was getting at: that anyone with enough money can get an initiative on the ballot by paying people to collect signatures, and once something's on the ballot, they can spend enough money to try to persuade people to vote for it. As a result, rich people and organizations can effectively buy legislation, or even constitutional amendments. That's not how the initiative process was intended to be used, but that's what we've got.

I'd also challenge you, if you're a fan of California's initiative system, to take a look at all the initiatives that have passed over the last 10 years or so. Now, remove the ones put on there by the state legislature (which is a lot of them), and of the remaining ones, ask yourself: how many of these represent a positive, populist change versus how many of them represent some corporate special interest or populist outrage attempting to do something that is more properly the responsibility of the legislature (like, in my opinion, the three-strikes law or sex-offender laws) or even just out-right discriminatory laws (like the various illegal immigration ones that have passed)? My personal calculus has been that the initiative process has, on balance, done more harm than good.