Let the rampant opinion commence: 10 questions. Agree, disagree?
1) Does erotic romance have an identifiable and unique quality apparent in its content, presentation, writer, publishers and market?
2) Do some readers read erotic romance but nor other types of romance or other types of erotica?
3) Is erotic romance a significant and substantial force in publishing large enough to suggest it is a genre in its own right?
Yes. And in e-publishing, even more so.
4) Is erotic romance a category routinely used by distributors?
No. Erotic romance generally shelved under romance, and sometimes under erotica or other areas. Erotic content is generally treated as a theme or rating within romance.
5) To be a genre must a body of work be uniformly appealing, or even acceptable, to all of its fans?
6) Is erotic content in romance new... romantic content in erotica?
No... and not entirely but you could argue that genre-romance themes in erotica were, until recently, rare. Erotic themes in romance were less overt but I certainly recall seeing ample amounts over the last 30 years.
7) Is erotic romance not romance?
8) Is erotic romance not erotica?
9) Is erotic romance a genre?
10) Is erotic romance a sub-genre?
Yes, of both romance and erotica.
In terms of romance, erotic romance is a rather large and demanding offspring that is making the nest uncomfortable for others and starting to piss off Mom (as adolescents often do). In terms of erotica, well--I think he would count as an absentee father on the whole (Wham, bam, thank you bottom line).
I can actually conceive of works that would be erotic romance without meeting my own definitions of either one of the parent genres but they are rare enough not to invalidate general taxonomic categories (Liger, anyone?). I could certain conceive of most erotic romance not meeting definition constructed by other specifically for their purpose of excluding them. But I think it is those narrow definitions that are at fault.
So erotic romance meets all the positive definitions of being a genre but not to the extend that it has stopped belonging fully to the parent genres--some taking more after one than they other, and a certain number who look suspiciously like uncle Bob (the western, thriller or come other genre). That makes it a sub-genre in my book... albeit not a submissive one ;)