Speaking as someone who has been through this (recently) and lived to tell about it: my daughter, now 2 years old, was just like that. Terrible sleeper, day AND night, and went through a terrible clingy phase. Everyone told me to put her down, let her cry, blah blah blah, or else end up with a terminally clingy, socially maladjusted child. Well, I went with my gut, listened to my baby, fulfilled her needs, (even at the expense of 2 years worth of a decent nights sleep, dates with the hubby, etc), and now I have a 2 year old who is incredibly secure, self-confident, marvelously attached, and who separates from me easily as needed to stay with babysitters and to go to preschool. I'd be sleeping much better at night except now I have an 8 month old going through the same darn thing. (oh well, at least the dates wiht the husband are back on...we just bring the little one with us!)
Contrast that with a little boy who is in my 2 year old's preschool class. His mother told me, a bit smugly, how she used a sleep training method to get him to sleep through the night by 8 weeks, and made sure to leave him with people often, from an early age, to "get him used to it." It is now 4 weeks into the school year and that child is still hysterical every single day when she drops him off, and again when she picks him up. Sure, I'll never know what "caused" either child to become the way they are, but I do know for sure that meeting my baby's needs, no matter how exhausting (24/7 for her first 18 months!!!) has NOT created a clingy, spoiled monster...quite the contrary. Hope that helps!