<<A minority of one cannot filibuster by himself. Even if the Democrats do not have 60 votes, they can compromise with enough Republicans to get the cloture vote and avoid the filibuster. A filibuster threat only works if you've closed off negotiations to enough people that you cannot get cloture.>>
The Republicans will vote en bloc against Obama's health care bill. There was some hope that Olympia Snowe would support the bill, but that's now gone. If one single Republican filibusters, he's one man from a minority contingent and he is holding up the passage of the bill, whereas there is no one man representative of any minority faction who can swing the election to Coakley's side if a bare majority favours Brown.
What you have in the filibuster is a mechanism whereby one man (perhaps it was inaccurate to call him a minority of one) representing a minority view in the Senate can block a vote that the majority wishes to hold.