More often than not, those who accuse others of being like the Pharisees do not know what a Pharisee is. They are often seen as just a bunch of religious nuts who took their faith too seriously, and tried to force it on others. Thus, Christians who take the Bible seriously are often accused of being Pharisees.
In reality, their zeal for their faith is about the only compliment the Bible ever gives the Pharisees. Arrogance and self righteousness was their main flaw (see the parable of the Pharisee and the Tax Collector in Luke 18:9-14). But another flaw the Pharisees had, far from taking the scriptures too seriously, is not taking them seriously enough.
The Pharisees were well known for their constant additions to the word of God. Some of these were actually good traditions. For example, the word of God forbade beating a criminal with more than 40 blows, and so the Pharisees would only allow 39, reducing the risk of miscounting. This tradition, while not technically a command of God, helped obey the command God did give.
But other Pharisaical traditions were not so good. Jesus specifically scolded them for skipping out on God's command to honour their parents by "donating" to God rather than using their money to support their parents. These traditions are both absent from the word of God, and contrary to it.
The ironic thing is that those who most often accuse others of being Pharisees are exactly like that. The very reason they accuse people of being Pharisees is because they have just been rebuked for either not believing the word of God, or for sticking to their own, personal traditions.
Curiously, there is a flip side to this coin. Another group, the Sadducees, also existed at the time of Christ. Just like the Pharisees, the Sadducees didn't treat God's word very well. But in the opposite way. Rather than adding man-made traditions to the word of God, they would refuse to accept any interpretation that wasn't word for word taught in the scriptures.
For example, the Sadducees were especially known for their rejection of the resurrection. In fact, in Acts 23:6-9, Paul uses this division to cause confusion among the judges at his trial. Yet, despite the Old Testament not specifically teaching the resurrection by name, it quite clearly teaches such a concept. Jesus even tells the Sadducees they do not know the scriptures, and then shows them that the very way God refers to Himself in relation to Abraham, Isaac and Jacob shows the resurrection (Mark 12:24-27).
This is another mistake people often make. They can't find a concept in the Bible not because it isn't there, but because it isn't taught either by name, or word for word. Most tragically, some people make both the errors of the Pharisees and the errors of the Sadducees at exactly the same time!
As Christians, it is vital to know our faith. This isn't being Pharisaical, this is just stating the obvious. If God wanted anarchists, He wouldn't have given us scriptures. As it happens, He did give us scriptures, and it is not our right to add to, take from or twist them. Let us instead faithfully study them, and apply them to the best of our abilities.