I think it depends on what it takes to find out if your service is right for me, which is dependent on the type of product you have. For Zencoder, for instance

I think it depends on what it takes to find out if your service is right for me, which is dependent on the type of product you have. For Zencoder, for instance, I wanted to know if I can interface with their API, and do so effectively and easily. So Zencoder offers a free tier, but the encoding is capped at ~5 seconds. I can't actually use their service as a product, but I can use it as a test and development bed. There were competitors I did not evaluate because I could not evaluate them as easily. So the question becomes, what does it take for your service to offer a trial, so that I can determine it's value to me?