your are absolutely right and it's exactly what I thought. The only thing is better to do is instead of un-indexing them I'd rather set up canonical links for the tag pages if it's possible.

Should I let Google index tags? Positive? Negative

Right now Google index every page, including tags... looks like I am risking to get duplicate content errors? If thats true should I just block /tag in robots.txt

Also is it better to have as many pages indexed by google or it's should be as lees as possible and specific to the content as much as possible.

Cheers

I wish I could find out who put this link up ... the consequences - if you know what I mean:)

I just ran https://www.majesticseo.com report for back links and showed me that I have one link at porn site ... not sure if it will be appropriate to post it here. The link was discovered on 03.05.11 and when I visited today link is not there... I dont know who put that link there.

Can I get penalty for that from google?

Can it be a mistake?

http://www.seomoz.org/beginners-guide-to-seo/basics-of-search-engine-friendly-design-and-development

go to the chapter 4