I really completely agree -- I personally do both. I purchase seeds when it's a variety I really truly want to grow. But I trade seeds too, primarily for varieties I'm interested in but not quite enough to purchase -- or for rare varieties that aren't commercially available anymore.
The ironic part is, of all the tomatoes that have ripened in our garden so far, this faux PBTD is one of the most tasty! Too bad I have no idea what it is.
Kathy