Blog passages and Copyright on book

It isn't a copyright problem, but it's potentially a problem for other reasons (for example, some publishers may look askance at being offered rights to a book which has had several "half-chapters" previously published online). But it can sometimes have some advantages, too, depending on many factors: it's rather a big and complicated issue (but not really a copyright one, per se).

Posting samples of your books is an accepted form of advertising of your books. Amazon puts up the first tenth of each book, B&N does something similar.

Neither minds that I do the same on my personal web site, because I also put links to their site so that those who like the sample can buy the full book from them. They lose nothing and gain sales.

It would depend on whether or not the publisher was seeking 'First Right of Publication' for your book. If your work is published previously elsewhere, it could prove a problem for them.

However, if your book is accepted, you could find yourself being offered the recent newer split style (but still rare) publishing deals. This is where you - as the author - personally get to keep online publishing control (such as sales through kindle) and the publisher controls the publishing rights offline (via book stores).