What are the pros and cons of forced marriages?

By "forced" marriages, I assume you mean arranged
marriages. (I cannot imagine any benefit whatsoever to a forced marriage.) The
advantages of an arranged marriage over a "free choice" marriage are many.  Couples who
marry this way have much more reasonable expectations than couples who choose their
partners on their own, and consequently, are generally much happier in their marriages. 
With a partner of one's own choosing, in Western cultures, the partner is expected to be
the perfect everything, and of course, that is not a realistic expectation.  Arranged
marriages also have all the power and resources of family, community and culture behind
them, shoring up any shaky moments in the marriage.  Generally, in cultures where
arranged marriages occur, divorce is more difficult and thus, couples tend to work out
their problems.  Certainly, the divorce rates are strikingly lower than in countries
where there are no arranged marriages, as you can see by clicking on the link provided,
which also has other interesting information on the differences between these kinds of
marriages.

I recently had a student in an arranged
marriage.  She and her husband are quite happily married and have grow to love one
another deeply.  We had an interesting discussion in class one night on this topic, and
one thing that was clear to all of us was that in a culture in which marriages are
arranged, people do not usually regard this as bad, and in many cases regard the
arranged marriage as a positive cultural phenomenon.  In fact, the idea of choosing
one's own partner on the basis of falling in love was a deeply alien concept to my
student.

The disadvantages are likely to appear when people
are so incompatible that their families and communities cannot cure the problems.  Such
incompatibility can take various forms.  One might be age and another might be
socio-economic, although most arranged marriages take place between partners of
approximately the same socio-economic status.  From the Western perspective, the idea of
not having a choice is deeply disturbing and offensive, but this disadvantage seems to
me to be more rooted in a cultural difference than it does in the concept of the
arranged marriage.