I would agree with all of the above _EXCEPT_ point number three.
Screw the phone home stuff - build a serial number generator and call it good.
I used to work for a prominent software house that made plugins for Illustrator, Photoshop, etc, and that's all we ever had. The pirate networks had figured out our algorithm, but who cares? They were never our customers in the first place. And for support, we required our callers to give their serial number before we would help them - we kept an account of which serials had been sold, so it was easy to cut off the freeloaders.
Go with an offline serial scheme that is non-obvious, but simple to code and you will be fine.
Bonus points - if you are doing online sales only, use the customer's CC or PayPal ID or whatever as the salt against a serial number for validation... you can not only spot pirates, you know where they got their copy.
Extra bonus points if you embed that hash into the IPTC or EXIF data of exported images...
from an interview with Kai Krause in 1994:
CJ: Japan has traditionally had a problem with software piracy on a home user level: users passing along copies of programs to their friends. Do you have problems with this, and what do you do about it ?
Krause: Yes, many people do steal the software and copy it. It's a very tricky problem for software manufacturers. But what we keep saying to people is, it's OK for their friends to use something, and play with it to see what it's like. But we appeal t o them that, "If you use it more than once a week, or if you do a serious project with it, then you should invest in your tools, and help those that make the tools to make better tools." So with that ethics angle, we find a lot of people understand that a nd buy the software. We get a lot of letters from people who say it's the only program they ever paid for. It's OK with me if they give it to a friend so they can at least see what it is like -- but it is a little tricky in Japan.