Shameless Promotion...and making a good impression
I suppose it would be indiscrete to mention names since the person inspiring this post didn't ask for advice...but once again I've seen a description of a new book in which the author didn't take care to make sure that spelling, punctuation and grammar were correct.
The blurb you create for your book is the first example anyone will ever see of your writing. It's important to make sure it is letter-perfect. It's no different than making sure you're well-groomed and neatly dressed when going to a job interview: first impressions can make all the difference. Someone seeing a poorly written description has every right to wonder: "If this author can't take enough care to make sure that three or four sentences about their book are written carefully, how good can the book itself be?"
I believe that half the time this problem could be solved if the author were to simply re-read what they've written before posting.