Multiple indexes or multi-column index?

Given a large (100,000+ rows) table such as:

CREATE TABLE foo (
  a INTEGER,
  b INTEGER,
  c TIMESTAMP,
  d TEXT
  /* possibly several more columns in here */
);

What are the pros and cons of these two different approaches to indexes?

CREATE huge_index ON foo (a,b,c,d);

vs.

CREATE a_index ON foo (a);
CREATE b_index ON foo (b);
CREATE c_index ON foo (c);
CREATE d_index ON foo (d);

--
Jeff Boes                                      vox 269.226.9550 ext 24
Database Engineer                                     fax 269.349.9076
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