One thing I forgot to mention in my post on modern day Pharisees is the danger of committing blasphemy of the Holy Spirit. First, let me give you a definition. To put it simply, to blaspheme the Holy Spirit is to attribute the work of the Holy Spirit to the Devil. This is what the Pharisees did when they accused Jesus of casting out demons by the power of Beelzebub. Although I think the definition could include other things (such as a willful and final rejection of Christ), this is the immediate context where Jesus discusses the issue (Matthew 12:24-32).
Do we have a counterpart to that today? I believe those who say that speaking in tongues is of the devil come dangerously close to this. Please note that I am not referring to the average cessasionist (a person who believes that miraculous gifts such as tongues, healings, and prophecy ceased at the death of the last Apostle). Most cessasionists at least believe that Pentecostals and Charismatics are their brothers in Christ, even if they think they may be a bit misguided. What I am referring to are those who say that any miraculous healing, gift of prophecy, or speaking in tongues must be attributed to the devil. Nowadays, this is a minority position even among non-Pentecostals and Charismatics, but there are still some who believe this and I think they are dangerously close to committing blasphemy of the Holy Spirit. Only God knows whether those who say such bold statements have actually committed this particular sin, but I would rather be safe then sorry when talking about miraculous phenomenon. When evaluating particular manifestiations, it is better to say "I don't know" than to run the risk of attributing a genuine work of the Holy Spirit to the Devil.