Porn and Gambling will be the two best areas to focus on IMHO.. And creating an easy mechanism for people to purchase coins (dwolla is great if you're in the states, I'm in Canada so my options are rather limited).
The economy needs to grow, spending coins on real goods and services is essential, I'm thinking of offering consulting services for website owners and pricing in BTC at a discount to encourage use - thoughts?
Economically speaking, yes - for sure. They fit the model. So does silk road despite what others day. I think international transfers definitely. Target young people travelling - beats the hell out of western union if you do a bit of planning first. Charities - I can see that- but people like the tax dedications so good for lots of small donations. Might be good for political parties looking to hide the source?
Other things I can see are youtubers with the link under their videos asking for support. I think its got potential for a lot of people to give a little because of the non-existent transaction fee.