posted by damon .
A collective noun is plural when the group acts as a unit (i.e., "The team lost their fourth game in a row.").
We tend to use a singular pronoun when a group acts as a single unit or the responsibility is taken as a group. So to use your team example, we might say "The team is posing for a photograph." as they are posing as a group. On the other hand we might say "
"The team are signing autographs." because they are doing this as individuals.
When dealing with teams in sport we subtly differentiate between true teams (e.g. soccer) and collective teams such as the Ryder Cup team. Thus "The team lost their fourth match in a row." could be a chess team.