Years affected are 1995-2008. In the rust belt, 95-2000 trucks were bought back by Toyota (I had a 1998 that Toyota paid me well for), the 2001-2008 trucks get a new frame and related parts.
Frankly, it depends where you live. I live in NJ and have lived in VT. A 5-10 year old vehicle here can be subjected to significant rust issues and you have to be very careful when buying a used vehicle. From what I've seen while traveling, I would not hesitate buying a 20yr old Toyota truck in Arizona, with faded paint. Of course I would do a thorough look at the frame and other parts but you just don't have vehicles crumbling to bits in the western part of the country.
For example. I was not actively looking to replace my 2001 Regular Cab Tacoma. It was in perfect mechanical shape, had a new frame installed 2 years ago by Toyota. I happened across a 2006, access cab 4cylinder 5spd 4X4 with only 73k on it and it actually had a fresh frame and related parts done in August of this year. I worked out a decent deal on the truck and I'm happy to have a truck with half the miles and significantly more cab space. I wouldn't even think about getting a 2001-2008 truck without the frame being replaced prior to buying it. That's on the east coast, in the rust belt. In the rest of the country, I would be less worried. I would not have bought the 2006 if it did not have the recent frame replacement.
On the other hand, I bought a 2009 quad cab short bed in July with 34k on it. I'm not worried about the frame yet, there is no rust to speak of and the truck looks brand new.
So my wife and I both have newer Tacoma's with no rust issues to worry about for a good 10 years.
When you go to look at a truck, bring a hammer to hit the frame with unless of course you can still read the Heavy Part sticker on it like mine.
Cheers,
Jorge
