Do you have to ask permission to use another blogger's posts?

If I see something cool on someone else's blog and I want to show it on my own, could I get sued for using their post without their permission? Or is this considered "Fair Usage" if I comment on it?
Do you have to ask permission to use another blogger's posts?
There are a few situations that are covered under fair use:





1. Primary and secondary school teachers using photocopies of short handouts for classroom purposes.





2. People recording TV shows on their VCRs or DVRs for future viewing.





3. Quoting short sections of an article or book for the purposes of analysis or commentary.





In terms of reproducing blog posts, I think you should be more concerned with the ethics of it than the legality. The chances of a blogger prosecuting you successfully for infringing copyright are slim to none.





But it isn't really courteous or ethical to reproduce someone else's blog post in whole. If you want to say "this is cool," then just post a link to the original blog post. If you want to comment on certain sections, you should quote those appropriate sections and then post your comments.
Reply:You do not necessarily have to ask for permission, but if you are gonna use someone else's blog post, at least reference them and link to their blog.
Reply:It would be wise to ask. It might be considered "fair usage" if you cite the source, but I'm not 100% sure.