For me, it was while trying to pre-board an overcrowded flight to Miami with a noisy baby in my arms, only to be ordered back in line by a curt agent.
They'll be able to tell you whether the property suffers from things like damp, or whether the landlord or letting agent is easy to get hold of when issues arise.
It tells the story of Joe Alston, a retired literary agent who feels that "he has gone downstream like a stick, getting hung up in eddies and getting flushed out again, only half understanding what he floated past, and understanding less with every year.
Al-Jazeera is not an agent of a state, and few (except perhaps the US military) would claim that it is an agent of Bin Laden.
But it is not the first time journalists have been deliberately targeted: Serb television was bombed during the Kosovo conflict because it was seen as an agent and advocate of state terrorism.
A Labour party member from 1950, he had acted as an election agent in 1959 and was elected to the local council in 1966.
The Observer has learned that the leader of the gang is a highly-paid British agent who joined the Loyalist Volunteer Force to foment sectarian strife in his native north Belfast during the 1990s.
The estate agent around the corner reckons an apartment like Gurlitt's would currently sell for up to €5,000 euros per square metre.
NGOs are also required to mark their publications with the term, and start any oral statement with a disclosure that it is being delivered by a foreign agent.
At first, Naipaul's literary agent (soon to be fired) judged the book too "cerebral" and, as the author sourly notes, "a year's work fetched only $25,000".
Of course, he doesn't have my voice to work with: look at me while I'm talking and I sound fine - some might even say impressive - but put on a blindfold and I suddenly sound like an estate agent.
