If a hacker is specifically targeting one person - then it's not that hard. We leave our 'footprints' all over the net. (try googling your own name or address)
A 'professional hacker will have software that will just sit there for hours trying different passwords.
'Profiling' someone will usually narrow down the type of password used. (close family names, birth dates, pets names, Address, Historical dates and places that mean something to the individual - it goes on)
They say - ( and i'm sure you've all read it somewhere) to mix up upper and lower case with numbers and especially punctuation - this makes it much more difficult for the hacker.