Help explaining very long exons in a dataset. - (Dec/05/2012 )

I'm looking at a dataset which contains all exon information for chromosomes 3 and 4 (human). Some exons appear to be very long. We've been asked to explain why this is so and if these are really exons. Is there a biological reason why there would be exons that are much longer than we would expect or is this a product of the sequencing technology?

Thanks for any help.

Do you know how the dataset was generated-- RNA seq, exon seq or genome seq?

I think it is genome sequencing. Though I could be wrong, all the question states is that they generated a table with all the exons in the human genome. It compares them to exons of people with diseases and this data was obtained with exon sequencing.