Granted, the same is true about everything else from the Google-verse connected to that Google Profile persona, so you need to be equally careful about establishing your Google Docs, Contacts, Calendars, Picasa photos, and other services in connection with an email address you don't own, or that you might not be able to access in the future.
There are ways for me to add additional email addresses to my Google Profile, or I could set up my Gmail account to automatically forward all email to my primary email account. I am sure there are a variety of potential workarounds to serve as Band-Aids. But, they all rely on the having access to the email account connected as the primary for the Google Profile, and for some people that may not be an option.
That is one reason I am not a fan of the integration by default with Google+, and I find the pervasive weaving of the social network into all things Google to be creepy . I am just dabbling with Google+, and already I seem to have a lifelong commitment with the social network that I can't easily change.
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