In my mind it comes down to how users already behave. The ones who like having lots of tabs open are probably used to choosing to open the link in new tabs, while the users who don't like it are annoyed.
I for one love opening lots of tabs (at any one time I have 40 or more tabs open in Firefox), so it might make sense to have my blog conform to the power users. But then i got to thinking about how I usually open links, and I realized I'm used to forcing the issue by ctrl-clicking, right-clicking, or in some way choosing to open a link in a new tab.
Here's why I do that: Of all the sites I visit, I can't tell you which ones have their links set to open in new tabs. Some do, but enough don't follow this rule that I am in the habit as a user of forcing the issue to suit myself.
I figure that everyone who likes opening new links in tabs is probably used to forcing the issue, and that means they will not be inconvenienced much by the change on this blog.
That would suggest that the benefit to making the change outweighs the potential loss.
What do you think?
P.S. Don't worry about the work involved. Making the change will take only a couple minutes to edit all the links. But once I have done so it will be terribly difficult to switch them back, so this needs careful consideration first.