This should be easy because there are just two things to write about. Customer Complaint Servicing over Twitter makes me uneasy because:

• I think it allows companies/brands to be lazy and delay the putting up and adhering to a complaint/trouble ticket tracking system. Since being able to handle queries/complaints/praise over Twitter and other 'social media' seems to be very 'in', it is easier to go with the crowd pleasing part than actually get down to the nuts and bolts and ensure that all complaints are tracked with the intent to improve delivery and performance. I've seen this approach far often. A ticketing system isn't stone age. It is a fairly decent way to keep documentation and audit trail of performance of various organization units. Not to mention that it is a great document trail should something end up in litigation (I am yet to read about a Twitter timeline being used in consumer courts). And, although sometimes brands/companies do end up doing a great job on the social media touch-points, more often than not there's a ham-handed, by-the-template response (a favorite example of mine being the Airtel handle on twitter @Airtel_Presence !)
• The other aspect is something that follows from the point above. I get the feeling that this exaggerated emphasis on social media driven and social media centric customer handling is discriminatory. Surely not all the customers of any brand would be interested in raising issues over such medium ! Most of them expect a standard set of ways (phone, email etc) to raise their issues. If social media driven cribs/complaints get quicker resolutions (and, I suspect that they often do since the pressure to appear responsive and responsible is enough to incite action) then the company/brand is doing a bit of disservice to a large segment of its population.