All the eggs in one basket

Would you seriously trust a 3rd party computer in this day and age? I have a complete aversion to entering usernames and passwords into computer I do not own. You have absolutly no idea what's installed on the machine, software or hardware (I dont buy the personal bootable CD as a serious privicy option given you have no control over the hardware). It always amazes me when I go on holiday to remote places, when you get to a town people run into the nearest internet cafe to check their hotmail, I bet most of these machines are running hacked versions of windows, with no security, and probably full of spyware...

Example 1:
you have an email service. You dislike the quality of the service and you want to move to a new one. How do you bulk transfer your messages from one service to the other one via webmail? You don't.

Example 2:
you receive email on 2 different email addresses on different services. Say you have an office email and a private email. Now your colleagues know both and by mistake often send you private emails on your office address or the other way round. How do you organize your email (e.g. moving private messages in the right place) via webmail? You don't.

Example 3:
You do not trust your provider and you want to back up your email periodically on your local system. Or you do not get "infinite" space from your provider, so you need to clean up things periodically, but you also want to store somewhere your old email. How you bulk transfer messages from the server to local storage via webmail? You don't.

Example 4:
You have 5 different email addresses from different providers because you have many affiliations. How do you keep them under control all from within one window with webmail? You don't. How do you avoid having to learn to use 5 different interfaces with webmail? You don't.

So the conclusion is that webmail is typically easier to deploy (and thus a nice solution to have), but it can offer you only an extremely limited subset of what IMAP offers.

[By the way, this is why it is truly sad that some email providers such as gmail do not give you an IMAP access but only webmail or pop.]

Unfortunately when there is a possibility to chose between two options, one with severe limits and the other one without, most people not only will happily choose the first (that is legitimate), but will also implicitly pretend that having two options is useless complication.

The result is that rather than defending the freedom of choice (in this case suggesting that an IMAP client should be always installed/installable alongside a browser wherever needed), the best that is done is often to invoke hacks on the limited solution to overcome some of the limits. The problem is that often the limited solution is _by design_ hardly adaptable to new behaviours. And furthermore, by removing some of the limits often it becomes as complicated as the original unlimited one.

As a final remark, note that it is in fact quite easy to have anything running anywhere without installation. For instance think of vmplayer virtual appliances.