Thanks. I was always confused about my email's subject line but the post your mentioned above gave me some idea. I approached around 7 bloggers in last 4 days with personalized pitch with different subject lines but didn't even get a reply.

I tell them 4 things : 1. How I found them (like read your post regarding Pinterest tips on XYZ.com) 2. What is Pinwoot? And why we started? - 5 lines 3. Traction info - 2 lines 4. About me and my cofounder in 2 lines.

I will be using tips from link you gave. Lets see how it goes.