I think that love and sex in a relationship can be two different things. I have been in relationships where I have loved my girlfriend and wanted to have sex with her, however I have also been in relationships where sex and love were two different things completely. I have very much enjoyed sex with some girlfriends and enjoyed their company, but would not call what I felt for them as "love." I have also loved and intensely cared for the girl I was with, but came to the point in the relationship that the physical attraction just was not what it had been. It was unfortunate, but true.
So yes, I think that they can be two different things. What does everyone else think?
If I'm in a relationship (committed) - there better be love. I think love can sustain a relationship in ways that sex cannot.
If you're in love and sex has to fall by the wayside (due to illness or ageing), then the connection can still be fulfilling enough to stay. The only caveat to this is that it has to be a genuine soulful connection and romantic love that you're feeling for your partner - not this platonic watered-down affection that people in sexless marriages often profess to feel. That's not going to keep you happy for the long-term.
Just fucking someone you're not in love with will tend to lose its excitement over time, which is why its best to keep those things casual and not 'over-promise'. It can be fabulous as far as the physical rush goes - and hey - sometimes we need that and don't want the hangup of emotional attachment.
The ideal relationship, as others have said, obviously have both love and sex.
If you're separating them, you're doing both wrong.
There is as much distance between love and lust as there is between sky and land. People don't know if there is love or lust in their mind. There can't be lust at all in pure and true love.
Sex and love in this world exists in a 1000-1 ratio. Falling in love is like catching a fly with chopsticks.
When the debate is lost, slander becomes the tool of the loser. Socrates Dancing_Doll so well put. I totally agree.