The worrying thing about Gmail is the fact that they will index all of your emails and create a profile of you which is linked to their search engine and advertising business.
I've heard people say this before, and I can't understand why this is a bad thing. Surely the whole reason why junk mail is annoying is because it's of no relevance to me - if Google can build up a profile of me which means I only see adverts which are of interest to me isn't that a good thing?
At least Google are being upfront about how they'll eventually make money from Gmail - Mailnation look like the 'totally-free' ISPs which there was a flurry of a couple of years ago, promising the earth for nothing and then collapsing under the weight of their failed business model - ie a bunch of chancers.
I have to agree with Mark
Gmail rocks.