Japanese Manga

Saw a news report this morning about how there are more n more folks who prefer to buy the entire volume of a particular manga series rather than waiting for each one to come out.
The reasons they give are so that they don't have to be kept waiting in suspense for the next edition and also so that they can relax for a whole day reading the entire volume.

While manga can be found at the book stores, its difficult to find complete sets which is why there have been quite a few sites that have been popping up like Mangazenkan and Otonagai - more from this google search result too.
I'm not particularly fussed but if I start a new series late and enjoy what I read, I usually try to get all of them in one go. How about you?

And how about anime? Do you prefer to watch as each episode is aired so you can keep in the loop with what others are talking about or wait until the series has ended before starting the marathon?