While there are no doubt many worthwhile causes that I agree with promoted by groups like 38degrees, there are some that I don't agree with or don't think are worth supporting.
The problem is how to decide which is which.
I'm not willing to blindly trust any organisation to decide on my behalf what is worth campaigning for by giving my support after only reading a brief email. I know we're all inclined to believe simple ideas without much skepticism* if they align with our existing beliefs and I'm wary of making quick judgements that might reflect my existing biases more than careful consideration would.
The trouble is that I often find careful consideration of a new issue utterly exhausting. Most of these issues aren't obvious black and white judgements - if they were no one would have to lobby government or businesses to get things changed. It requires time and a bit of intellectual effort. The volume of emails produced by most campaign groups, Avaaz, 38 degrees or others, are impossible to keep up with for anyone with a job, family, social life and regular exercise.
For me the same argument applies to charity cold-calling. I never sign up to anything on the doorstep or street. I already have regular charity commitments and make one-off donations to sponsor friends - should I change these when a representative of another charity knocks on my door? The answer depends on questions like how efficient the charity is, what they've achieved recently, if they've been involved in any scandals and how closely they align with my values. Not something I can judge in a five-minute or even half-hour conversation.
I admit that by refusing to consider every cause or charity that asks for my support I may be missing out on something I'd consider very worthwhile. I'm not saying I'd never explore new causes or charities, but the burden of choice means I'd prefer to start with a recommendation from a friend or trusted colleague or a subject matter I already know something about.
This might all be made simpler by having some independent reviewer of charities providing open and accessible comparisons of their finances and achievements. Until it becomes a lot easier to decide my default answer will be a simple, firm "No, thanks".
* - I prefer Noah Webster's "American" spelling of skepticism.