i don't think there is a right or a wrong solution.
personally, i would use my site statistics if i wanted to see which pages were most visited
showing the customer 'recently viewed' items could be useful in securing a sale, but if this information is redundant for other customers (or the same customer on their next visit), then I see no need to store it.
(Saying that, i have written some code for showing the last items viewed, by storing the productid's in an array and can't (yet) get the records to display in the order in which they were viewed)
upselling or cross selling would usually involve storing data and can be very useful in increasing customer spend.
i can advise on these techniques if you wish.
hope this helps