I have been guilty of this in the past, and I hear pastors all the time say something to the effect of "We know that Jesus is here because He said He would be present whenever two or three of His followers are present" before or during their prayer. On one level, I do force myself to keep my heart in check because the spirit of what is being said is not inaccurate per se and I don't want to be critical of people's prayers.
But on the other hand I have two problems with this statement.
First, it is violates the first three rule of Bible interpretation: context, context, context! This is what the immediate context before states:
If your brother sins, go and show him his fault in private; if he listens to you, you have won your brother. But if he does not listen to you, take one or two more with you, so that BY THE MOUTH OF TWO OR THREE WITNESSES EVERY FACT MAY BE CONFIRMED. If he refuses to listen to them, tell it to the church; and if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector. Truly I say to you, whatever you bind on earth shall have been bound in heaven; and whatever you loose on earth shall have been loosed in heaven.
And this is what follows immediately after:
Then Peter came and said to Him, “Lord, how often shall my brother sin against me and I forgive him? Up to seven times?” Jesus said to him, “I do not say to you, up to seven times, but up to seventy times seven.
What is the focus of the passages immediately surrounding our text in question? Sin, correction, and forgiveness. Is prayer the focus of this passage at all? No. The point of "where two or three are gathered" is in reference to church discipline. I tell you there is nothing less appealing as a pastor than having to confront a fellow Christian about their sin. This passage is assuring us that in this process, Jesus is with us.
The second concern is what if I am one? Will Jesus only hear my prayer if I have a proper prayer quorum? No, that is ridiculous! Jesus' last recorded words in the Mathew (28:20), "...and lo, I am with you always, even to the end of the age." The Scripture makes it clear that we are to pray always about all things! God is there for us all the time! So why don't you pray to Him now? :)
I don't want to be trivial, but I do think there are many things people think come from the Bible and they don't, or they are not understood in context and are ultimately misapplied. As we interact with the Bible, we must take caution to "rightly divide the Word of truth" (2 Tim. 2:15)!