Yes, because you risc mechanical induced atrial arrhythmias. Locate the tip in the prox. Vena cava superior. Up to my experience there is no risc for cardiac tamponade. 

Yes. Obviously. Not for the risk of tamponade, but the risk of atrial arrhythmias. It's not neccesary to say anything else about it. The main problem is that most of doctors introduce the catheter too much (20 cm). It's enough 16-17 cm.

 The FDA guidelines regarding catheter tip location (catheter tip should not be in the right atrium). This is very controversial. Some researchers agree, some researchers disagree. According to an article on CVC catheter tip position, a catheter tip that has been positioned at the SVC/right atrium junction will rarely cause significant arrhythmias or vascular perforation. These complications may happen during catheter insertion.

I often blindly placed CVC in various acute situations, cardiac and metabolic, and I never had  any great atrial arrhythmias.  

I recommend repositioning it. The tip of the CVC in the right atrium would cause mechanical induced atrial arrhythmias. 

It is usually ventricular ectopy that I see if the Seldinger guidewire is advanced too far, I can't ever remember seeing atrial ectopy.  The guidewires we use (in kits from both Arrow and Edwards) are uninsulated metal.  Perhaps this is important in inducing ectopy?  I've never seen persistent ectopy even from a deep CVC once the wire is removed. 

I would agree that the risk of tamponnade is not a concern, and the risk of arrhythmia is not high, but certainly is a theoretical concern. If it's a non-tunneled catheter, it is easy to pull the line back a couple centimeters without compromising sterility. If it is a tunneled catheter, one could argue not put the patient through another procedure.

Tunnelled central catheter tips should, in my opinion, be sited just inside the right atrium.  This eliminates the risk of SVC stenosis and fibrin sheath formation - both of which are major problems in dialysis patients and those dependent on long-term TPN etc. Although I have no data to show that my 25 year experience has not led to atrial arrhythmias, I concur with the observation above that ventricular, rather than atrial arrhythmias are observed when guidewires are introduced.  These are invariably benign and self-limiting in my experience and to do with wire movement. 

Hickman's original paper title says it all: Surg Gynecol Obstet. 1979 Jun;148(6):871-5.

A modified right atrial catheter for access to the venous system in marrow transplant recipients.

Hickman RO, Buckner CD, Clift RA, Sanders JE, Stewart P, Thomas ED.