Except one: discovering new pages that are interesting for you, and adding them to your watchlist. (I have been editing Wikipedia for five and a half years now, and know what a watchlist is good for and what is not. Further, I have an own personal wiki on my computer and I use it daily happily fr organizing my data and thoughts.) The other main disadvantage is the lack of a global watchlist. Once SUL is being used for quite a time now in WMM wikis, a global watchlist would be very useful to introduce. Historically, global use with one account was not an initial concept of MediaWiki, but a later improvement that was implemented without a watchlist. The problem is to follow several wikis continuously. I see a setting for e-mail about the changes of my talk page and the LQT topics, not the complete watchlist; but let's suppose, you may get an e-mail about every change of every watched page, and be flooded by e-mail notifications, why is that better than real content e-mails? While on a mailing list people are reached directly and a question will reach everyone, on a wiki page less people will find the same topic. And again, what about new ones?

A good mailbox or a good e-mail client software gives you a great scale of possibilities, how to handle e-mails with searching, grouping, labeling, deleting etc. Did you know that Pegasus Mail was able to search with regular expressions many-many years ago? The only way of searching for something with regular expressions in MediaWiki is to run a bot which is not as fast as slow it is (I do that daily). In Gmail, you may create plenty of labels and sublabels, in mailing clients plenty of folders and subfolders, while in a wiki you have only one watchlist that shows the last 7 days which is not a happy thing after a holiday or a longer period while you are not able to follow events here, but e-mails will wait for you.

There are a good many things that are really not for ethernity, and each member of a list can decide to delete it alone if he/she is no more interested in, while these topics remain on a wiki.

Isabelle, it is nice to see your enthusiasm. After 5.5 years of being a hardcore Wikipedian and after 17 years of heavy use of uncountable mailing lists in several topics, I really like both forms of communication and both fascinate me, and I can compare them and I see advantages and disadvantages of both. But you may still try to convince me that a wiki is the best form of communication. :-) As I told, in my opinion it is primarily for storing content.