I remember really wanting stickers from Digg, Twitter, etc. back in 2007. I sent out a bunch of emails saying that I was at university and wanted to promote their cool sites with stickers on my laptop (I thought I'd be cool and have a bunch of tech stickers all over my laptop) and I did get a response from them all, most sent me free stuff. T-shirts? Never tried, but that's quite a bit more costly... Really depends I guess, but I wouldn't count on a formula that'll work every time..