What was the first topic of conversation in your office on the Monday after Live8? Were people saying they'd been really inspired to get more deeply involved in Make Poverty History? Or were they banging on about how fantastic - or disastrous - Pink Floyd had been in their declining years? Shortly before the concert, Eddie Izzard cheerfully admitted that, although he supported MPH, he didn't know much about the cause. And after the G8 summit, Bob Geldof blithely gave the politicians eight out of ten for aid and nine out of ten for debt relief, a more generous assessment than many development agencies would have made.
These are just three ways in which celebrity support can prove less than entirely useful to an important campaign: supplanting the message, not bothering with the message and hijacking the message. There are others, such as the risk of the artist you've just recruited being worked over by the tabloids for snorting cocaine or being caught making racist comments.
The usefulness of celebrity support is under active debate in the MPH coalition, and the assessment is not universally approving.
The debate is doubly significant this week as the year's second big campaign, Stop Climate Chaos, gets under way. Charities will no doubt be taking obvious precautions before signing up celebrities, such as making sure that they don't have a six-litre 4x4 gas guzzler and an executive jet in the garage. But the involvement of the famous will bring similar hazards to those encountered by MPH.
As with most tricky problems, there's no simple solution. Very few charities would want to opt out of the fame game altogether: we live in an age obsessed with celebrities, and many of them support charities with genuine commitment and can produce invaluable publicity - not to mention donations. But there are duff ones too, who are more interested in raising their own profiles and whose attention spans may not stretch to the complexities of the situations in which many charities work.
Fortunately, charities seem to be getting a bit more hard-headed and discriminating. The bigger ones employ artist liaison officers, who have become skilled in checking out, recruiting and 'keeping warm' their banks of stars. One rule of thumb could be that if celebrities haven't the time or inclination to visit your projects and understand your work, you may be better off without them, even if they do offer the prospect of quick 'win'.