Never been fond of that whole transporter creating life thing when people get duplicated (ie. Kirk, Riker). This is a big reach (I am fond of those), but in a universe full of strange aliens lurking nearby in subspace or an alternate dimension of the week, I can see one being "overwritten", either inadvertantly or by choice, by a transporter used in appropriately eccentric local conditions.
As to how much info storage a transporter needs, it's easier to see a "pattern buffer" as a sort of holographic storage device (and none too shabby starting point for a holodeck) that stores the quantum wave pattern intact. This means that technically no atomic bonds have been broken (ie. you haven't destroyed the transport subject more completely than any weapon system) and Lt. Barclay still retains some aspect of himself for grabbing things in transit in that TNG episode (The Greatest Fear?). If you just temporairily remove the matter "slurry" (ie. the "particle" side of things) from the pattern and make a gross adjustment to its quantum characteristics so that it's more at home at the other end of the transporter beam, the pattern can be "re-imposed" on it at the target point. I can see that up and running in the mid 22nd century without needing to store all the info to reproduce something or someone atom by atom. Sufficient info storage and manipulation tech for biofilters, replicators and holodecks can be left to the mid 24th century or so.
On a related note, you'd could say that 22nd century "protein re-sequencers" are simple matrix precursors of full blown replicators which require a fixed input medium to which a single phase, fixed molecular "re-alignment" is applied. As an unsavoury yet green side note, I got the impression they tied into the NX-01's waste treatment system.