Slacktivist. Love the word, just love it. Gutted that it wasn't the Oxford English Dictionary's Word of the Year, though it was shortlisted. If you're not keeping up, here's the definition: "one who engages in digital activism on the web which is regarded as requiring little time or involvement". The classic example is the famous "Bring Back Our Girls" campaign in response to the kidnapping of the Chibok schoolgirls by Boko Haram, which involved millions of people clicking mouse buttons and posting selfies, and achieved precisely nothing.

Bob Geldof is not exactly a slacktivist. However, I'm afraid that he is the cause of slacktivism in others. The latest incarnation of Do They Know It's Christmas, aimed at helping to fund the fight against Ebola, is out and is doing extremely well. The single itself raised £1 million in only five minutes. Jolly good. Geldof has been accused of trying to assassinate the character of the singer Adele for allegedly refusing to appear on it, rather convincingly denying it. In any case, it's hard to get mud to stick against St Bob.

Here's the thing, though, and here's why I'm not buying it. First, Ebola's the wrong target. It may be counter-intuitive to say this because the numbers are still going up – but actually, the world is already winning the war against it. What's really significant is not the number of total cases – which will always rise until the disease is eradicated, if that were possible – but the rate of new infections, which is dropping. So new infections in Liberia's capital Monrovia are down from 75 a day in September to only 25 a day now. Hans Rosling, a professor of global health who works in Liberia, told the BBC: "This means we are fighting a low intensity epidemic. It flares up in one of the countries, it's controlled there and then it jumps up in another place. This will take time to get rid of." But, he says: "We only know one thing – we are going to win. We are talking about months."

That's not to say efforts don't need funding. But compare that with HIV/Aids or malaria. Malaria kills 6,000 people a day. Aids kills 2.5 million a year. The difference is that these illnesses have become normal. The numbers are too big. They are statistics, not tragedies. They have not the power to seize the imagination and so they do not attract the attention of celebrities. So why does it take Ebola to provoke another single?

Second, we're being sold a false model of charity. The point about charity is that it is caritas, unconditional love. In the celebrity model, we are being entertained: buy a recording, enjoy the music if you like that kind of thing, and you've given to a worthy cause. Only you haven't; you've paid for a product. The giving (let's not be churlish, now) was the hour or two the singers gave up to appear in the studio. This is a world away from the real spiritual discipline of giving, which is costly, disinterested, and if possible anonymous (we only know that Adele gave to Oxfam because Geldof was reported as having attacked her, which he probably didn't).

I'm not quite enough of a purist to call for an end to such things altogether. Geldof has genuinely helped people. Without him, millions of pounds would not have been raised to meet real, urgent needs. And some of those who have volunteered for the latest charity warble have given money too, and genuinely care. (Others probably haven't and don't.) But in the end, clicking on a mouse button to buy a charity recording is good, but – well, not that good.

The danger of celebrity appeals like this is that they make slacktivists of all of us. What's needed is long-term, unglamorous, limelight-free, costly involvement in the causes that really make a difference. Malaria and HIV/Aids, for instance. Tax reform. Renewable energy. Clean water. These things are dull: but after the celebrities have had yet another moment in the spotlight and reaped their harvest of clicks, these problems will still be there – and so will the people working to solve them.