Now lets pretend for a moment that you want to get links from popular blogs by posting comments on them and including a link in the comment.
In my experience this doesn't work because too often people just spam comments that have little or no value and it is very obviously spam.
What then happens is the blog owners monitor the comments and then delete all the spammy comments and approve the comments which aren't spammy.
The end result is that spam comments don't work. It only annoys the blog owner and they will routinely, with a dose of anger in their minds, delete all the spam comments.
So then your client gets zero links from all that effort.
Lets pretend you even wrote a good quality comment. A nice long, well thought out comment. And then sometime during the comment you include a link to Italian cooking lessons in Toronto or whatever it is you are promoting.
I would wager apples to oranges that even though you spent all that extra time and thought writing something meaningful that half the time people will just delete your comment anyway. Thus such comments on blogs are not a reasonable way to promote your website.
Yes, you could spam the words private cooking lessons in the comment sections of websites... But you would probably just be wasting your time and annoying the owners of those blogs.
What you should be doing is contacting the blog in question and then offering to PAY THEM for a review or an advertisement for cooking lessons in Toronto or similar keywords. Having the keywords in an actual blogpost are 10 times more valuable because the topic of the blog post should be closely connected to cooking lessons, the name of the local city (in this case Toronto), the specific topic "Italian cooking lessons", and so forth. The quality of the blog post and the quality of the links will be dramatically better.
Furthermore people don't usually click on links within comments. But they DO click on links within the actual blog post.
Conclusions
Spammy comments = Bad
Paid blog posts = Good
To learn more about blog spam check out http://en.wikipedia.org/wiki/Spam_in_blogs
