Over at his "Neuf et demi" blog French comics theorist Thierry Groensteen just posted (what I believe is) an excerpt about webcomics from his forthcoming (in 2011) book on comics (a follow-up to his Systeme de la bande dessinée, translated as The System of Comics (UP Mississippi, 2007)). It's a mixture of clichéed anti-screen-reading objections and some more astute observations about the difference between reading comics online and reading them in print. Here's a quick summary with commentary.
1) The loss of the book as manipulable, tactile object. The classic complaint.
2) The closure of the work. In Groensteen's mind, reading a book is an enclosed, absorbing activity where you are never distracted by anything, while reading something on a screen is a constant state of distraction: surfing, messaging, listening to music. This isn't a case of the medium itself but the reader. It's just as easy to be distracted and unengaged when reading a book (think of anyone trying to read a textbook), as it is when reading on the screen. The factor isn't the medium, but the person and, even more, I would think, how interested/engaged they are with the thing they are reading.
3) The memory of location. This is an interesting one. In a book you have read there is a certain sense of place, where a panel was both in the book and on the page. One area of this that I do miss in reading on the screen is the sense of location one has in a book of where you are in: are you nearing the end? are you right in the middle? The screen lacks this, where every page seems (and does) exist in the exact same place.
4) Screenreading is ill suited to long works. While he thinks it is convenient to read short (say 30 page) works on the screen, those of lengthy immersion are less suited for screen reading. Ironically, the comics he mention in this context are Maus, From Hell, Cages, or Jimmy Corrigan. What do all those works have in common? They were originally serialized in shorter parts. I read the latter three in serialized form. Groensteen seems to overlook this (perhaps because I assume none of these were serialized in their French language versions).
5) Screens of differing sizes do not work for all comics. Computer screens can work for showing a whole page or even a two page spread (if your screen is big enough), but reading a comic on a mobile device generally means one of those panel by panel viewing applications. As Groensteen notes, this often breaks down elements of the page as a whole, and doesn't really work for panels that aren't of a very conventional rectangular size. I'm in agreement here, I really dislike that type of comics viewer. I do think these issues are (or will be) overcome on desktop screens though (since they keep getting bigger and cheaper).
6) The attractive qualities: portability, cost (generally cheaper), home delivery, quick access to new serializations, and of course the "almost magical fascination" that screens hold for people.
His summary: "While all these factors can explain the growing popularity of reading comics on the screen (a popularity which it is too early to decide if it will last), none of these could be described as an increase or enrichment of the work itself. For the connoisseur, attached to the language and aesthetic properties that comics have developed, the sense of loss must logically prevail."
I don't share Groensteen's seeming skepticism that screen popularity won't last (or perhaps I am just reading in to his statement), but I do agree that many elements of webcomics and screen reading have yet to contribute aesthetically to comics (and perhaps could be detrimental). But I do think, Groensteen almost completely neglects the economic, commercial, and social aspects of webcomics which are important to comics on many levels.