GMail

GMail is Google's Web Mail Service.

Google started off by offering several GBs of space for each mail account. This was amazing compared to the popular providers of that time Hotmail, Yahoo etc. offering a few MBs in comparision. Agreed that offering the huge capacity spurred the rest of the players to also up their offerings. But details of their service started emerging which felt foul of data privacy laws in several countries.

GMail offered the facility of store huge amounts of mail/data. This on its own is ok. But what Google does with it is highly dubious.

Targetted Ads :
GMail mail servers will "read" each mail and provide targetted adverstisements in each email.
They claim that the ads will be relevant to the subject/content of the email. Though the reading is (supposedly ?)done by an automated/non-human entity, it is still invading your privacy.

Storage for ever :
Given the huge space available, there is no real need to delete mails. But remembering the fact that the "adversiment" engine / data harvesting engine now has even more data to play with, it probably a bad combination. Also google is free to store even the deleted information for ever. The potential of abuse, using this information, is indeed very high.

Data Privacy :
Google is free to use the information it has harvested by reading your email to its own benefit.
What is Google going to do with such a huge amount of harvested data ?. Apart from providing advertisements ?. Maybe send you "relevant" junk emails ?. or sell your email id to "relevant" companies ? Possibilites are endless and quite worrying.