It is by no means scientific; it may be a very "US centric" list; and I have ignored second and third order effects.
Add the following numbers for yourself:
1. number of email accounts (include everything)
2. number of distinct credit cards
3. number of debit cards
4. number of social website accounts you maintain
5. number of IM/Chat/phone accounts you maintain
6. number of intranet passwords you have to remember
7. number of savings/trading/checking/retirement/legal accounts
8. number of online accounts with merchants
9. number of blogs for which you need login access
10. number of distinct internet/usenet style groups you belong to
11. number of news/info sites you browse with login access
12. number of hobby/recreation/professional sites with login access
13. number of company required login accounts (partner sites)
14. number of non-profit/voluntary group accounts/credentials
15. number of wifi hotspots you've connected to in past year
16. Add 5 for every cell phone
17. Number of off-work credentials to get compute resources
18. Add 10 if you have a secretary/PA to manage your calendar
19. Number of thumb drives, offline and online data backups you maintain
20. Add 30 if you predominantly use windows. Else, add 10.
21. Add 10 if you use google backend for anything.
22. Add 50 if you use linked in extensively, 10 if you use sparingly.
22. Add 500 if you use facebook extensively, add 100 if you use it sparingly.
This number is the equivalent of total "strangers" you interact with and share your private data.
At some point, you will have to manage these more carefully.