I reported these accounts to Google, but nobody seems to care. These people post comment spams (for example, delani posted the same stupid comment in 15 posts from my blog today):

delani – http://www.blogger.com/profile/16334491081307755729
(http://www.google.com/search?q=ebookhelper.blogspot.com)

wangyinfeng – http://www.blogger.com/profile/04825975768266641883
(http://www.google.com/search?q=wangyinfeng++-groups)

It seems trivial to detect if the same user posts the same comment multiple times a day... shouldn't they be able to automatically block that then? Or did they use slight variations in wording/ spaces etc.?

It's because of CAPTCHAs, more and more easy to crack...
Well, it seems there is no CAPTCHA on Ionut's blog.

Nope, the comments are identical and they are posted to many articles in a short period of time (although I don't think they are posted automatically because I enabled CAPTCHA and I still received the same comments).

Even though Blogger should add a clever spam filter, it's pretty easy to implement some simple spam detection rules:
* identical comments for different posts in less than an hour
* comments that include more than x links
* incoherent text
etc.

Here's delani's (in)famous comment:

http: //ebookhelper.blogspot.com/
E BOOKS
* ADO.NET (1)
* AdSense E-Book (2)
* Affiliate Ebook (3)
* AJAX (6)
* ANT (1)
* Archaeology ebooks (4)
* Architecture ebooks (4)
* Autobiography (2)
* Biography (5)
* Biotechnology (1)
* Business (6)
* C++ (1) (1)
* Civil Engineering Ebooks (3)
* Clinical (2)
* Comics (2)
* Communication Technology (2)
* Computer (8)
* Computer Hacking (2)
* Computer IT ebooks (2)
* Computer Magazines (1)
* Concept of Art (3)
* CookBook (1)
* Design Interior ebooks (3)
* Education ebooks (1)
* Electrical Engineering (2)
* Engineer (2)
* Engineering ebooks (2)
* Finance ebooks (2)
* For Dummies (12)
* Graphic Design ebooks (2)
* History (4)
* HTML (1)
* Insurance ebooks (2)
* Internet Marketing ebooks (2)
* Java ebooks (2)
* Java Script (4)
* Language ebooks (2)
* Law ebooks (2)
* Magazine (2)
* Magazine for Adult (1)
* Manga Comics (1)
* Mechanical Engineering (2)
* Medical ebooks (2)
* Money (1)
* Motivation ebooks (2)
* Net (19)
* Networks (3)
* Non Fiction ebooks (1)
* Novels (3)
* Photo (2)
* Physics ebooks (1)
* Psychology ebooks (2)
* Science (8)
* Social (1)
* Software Ebook (3)
* Software Testing (19)
* Technology (2)
* Travel (2)
* Tricks (2)
* VC++.Net (1)
* Vista (5)
* Web Development (6)
* Wireless (3)
* Write and Langguage (6)
* XML (1)

> although I don't think they are posted automatically
> because I enabled CAPTCHA and I still received the
> same comments

Wasn't there an article recently about how spammers break Blogger's captcha?
Ah, there it is:
http://securitylabs.websense.com/content/Blogs/3073.aspx

"I don't think they are posted automatically because I enabled CAPTCHA and I still received the same comments"
I don't see CAPTCHAs on your blog, Ionut.

philipp : Blogger's CAPTCHAs can also be broken thanks to audio
http://www.0x000000.com/index.php?i=560