Social (Classmate like) database schema appreciation
1. &nbsp; payment (black box)

1.1)&nbsp; No currency information?
In the Payments table, although you store an amount and date, you store no currency.  Perhaps you plan on only charging in one currency, but I feel that method will only last so long if this is intended to scale.

1.2)&nbsp; What is this second payments table?
What is the second payments table for?  The one below and slightly left of the actual payments table?
It seems to have only an id column, which is the only column in this diagram to specify a data type!?  I'm guessing this is some diagram artefact.

1.3)&nbsp; You'll need more than just the name to take payments!
The payment_methods table currently doesn't store the type (i.e. credit card, paypal, BitCoin, whatever) of the method.  There also seems to be no linked table of payment_types for this either.

You will need to store stuff like credit card numbers, etc somewhere  (hopefully not in this database!).  You will need some sort of linking information for those stored payment methods to be kept in the payment_methods table.



2. &nbsp; social (blue box)

2.1)&nbsp; Who exactly is me?
I'm assuming the Me table is some sort of façade or profile type of table.  Perhaps allowing a given User to shield themselves from the embarrassment of letting their collage/university friends see the Music they were into in high school? :P

I do not believe it makes sense to double store the first, middle and last names of the user.  It would be much better to go with a solution like that which @beeks suggested in the comments above.

2.2)&nbsp; My_Profile_Details... field?
I cannot figure out why this is a single field.  I assume it's some sort of memo type, for storing a lot of text (i.e. a CV of sorts).  I think this needs MUCH more decomposition.  At a minimum, into Sections of some sort.

There also seems to be nothing in a Proflie that allows a user to select what Schools/Collages/Universities/Enterprises they studied/worked at, etc?



3. &nbsp; classmates (red box)

3.1)&nbsp; Internationalisation?
This part of your design is missing information regarding country. Even if you're only looking for schools/colleges in a particular county, employers (which is what I assume Enterprise is for) may be in any country.

Also, If a classmate starts their own enterprise, do they have the same relationship to that enterprise as someone who works for it?

3.2)&nbsp; Institution Names
You have assumed Universities (and I suppose high schools, primary schools and collages too) have only one name, and that name is in English (or whatever language you're intending to store).
It is quite common for universities to have different names in different languages.  Institution names can also change over time (renamed, etc). 

3.3)&nbsp;Institution Decomposition
Not all Universities divide themselves into Faculties, some are simply a collection of Schools (think Oxford, etc).  These can also change name over time.  Also, both faculties (schools), universities (and probably collages, primary and secondary schools too) can merge (i.e. get taken over/bought out) over time.

3.4)&nbsp;Institution Location Multiplicity
Your design seems to assume a University can only be in one town.  Many Universities have different campuses in different towns.  Some even have campuses across international borders.