I say "delete" because whatever data you have placed in the hands of Google (or any other "big money" service) ceases to be your data and you have no verifiable knowledge on its whereabouts and its (ab)use. By this I mean that even if you decide to delete your account, in reality your data may still be kept by the companies, legally or not. There is no easy way to find out.
Good news for all oppressive regimes of the world. Twitter can now censor tweets by country, and ‘reactively withhold content from users in a specific country. [...] the removed content would be available to the rest of the world.’ http://www.bbc.co.uk/news/world-us-canada-16753729
So on top of sponsored tweets, here comes another “feature” we can all live without. Using Identi.ca (https://identi.ca) or any other microblogging site was never before so attractive.
Exceptionally, something reasonable comes out of EU politicians. It seems that the «Right to be forgotten» proposal could be one of these rare moments of lucidity, announced at a conference with a rather disturbing title: «Digital Life Design»...
In few words, the proposal means that people should have the right to ask for their data on social networks to be deleted, and companies will have the obligation to comply, ‘unless there are “legitimate” grounds to retain it’. (http://www.bbc.co.uk/news/technology-16677370)
This was to be expected: as Google wants to transition from a search engine company to a social network (after being overtaken by Facebook in the late 2000s), it terminates all the “unsocial” services, and integrates everything into or with Google+.