Interesting map; pretty good job overall. I agree with many parts of it, and it makes sense in general; I wonder how the areas in western Europe that have higher frequencies got it and through what people. Outside of Europe one would find Iranic peoples and north Indians also having high amounts. But there are some things I'm not so sure about for this version. Is this really the latest most updated one? Was there a high amount of samples that was fairly evenly distributed? One thing I find odd is how heavily you put the whole area of Romania as R1a while the rest of the Slavic Balkans has only low amounts in the 10%+ plus range. I know the northern and eastern parts of Romania have higher amounts, but I've never seen them quite as high as on this map before. Every study I've ever seen for them had them as a population at somewhere between 18-20-22% R1a, at most no more than 24 in one study, but it varies, so I'm just checking. I seriously doubt big regions of the country are in some of these ranges as on this map, and I don't think the vast majority of regions go any higher than 30, let alone the 40%+ range you included the northern part in. Even the official Eupedia page for the frequencies only has it at 18 % overall, but based on this map one would think the average would be over 30% for the whole, which I don't think is true
http://www.eupedia.com/europe/european_y-dna_haplogroups.shtml. There is, of course, in reality some "spillover" and transition in the northern border areas to Ukraine, Hungary, Moldova (which is normal), but the difference is fairly noticeable when comparing to most of the country. You made it look like as soon as you hit the border with Romania from the south you suddenly get much higher amounts of R1a, that grow every few miles you go northward, which I doubt, and it's not even like that; certain regions have different amounts. Also, I know especially northern Croatia/Slavonia, as well as Slovenia have considerably higher amounts of R1a than Romania from the heavy Slavic settlement there. It seems this map just accounts for broad , gradually changing patterns kind of emanating out steadily as concentric rings from the core region around northern Ukraine, Belarus, Poland, Russia area rather than precise areas of change.
I think the most accurate map I've seen so far is this one
http://upload.wikimedia.org/wikipedia/commons/7/7b/R1A_map.jpg, which actually breaks it down by regional subdivisions within countries and takes into account detail between areas. Most maps I've seen also put the northern Greece/Macedonia area as high in R1a yet I didn't see that on the one in this thread. There's parts of Bosnia and Serbia that have higher amounts also.
Also, I wonder how accurate these are as well
http://upload.wikimedia.org/wikipedia/commons/3/32/R1a-map.JPG
http://www.r1a.org/img/map.jpg
http://lukferi2.webs.com/R1a_distribution_Eurasia.jpg
http://2.bp.blogspot.com/__zYu2MdAxIk/SXE7kt-4uYI/AAAAAAAAB6E/oQ0-ik93i5A/s400/Picture+3.png
Romanians cluster more to the south and in the middle of the Balkan population cluster despite their more northern geographic location on most charts I've seen, which reflects the paleo-Balkanic origin and core basis for their people, with many Serbs, Croats, Slovenes, some Bosnians etc being more north toward cental Euro/West Slav populations.
http://www.nature.com/nature/journal/v456/n7218/images/nature07331-f1.2.jpg
Apparently the Balkans is fairly homogenous in most studies, with Aromanians being among the more distinct groups, but still not that much.
http://www.carswell.com.au/wp-content/documents/homogenous-balkan-analysis.pdf
Found these markers, this one relating to Mediterranean ones
http://desmond.imageshack.us/Himg833/scaled.php?server=833&filename=medb.jpg&res=landing
this for Baltic
http://img195.imageshack.us/img195/9767/relbalt.jpg
an interesting way of grouping people
http://oi44.tinypic.com/zygj7c.jpg
Anyway, I know R1a isn't necessarily only Slavic, but is often thought to be linked to some kind of Indo-European migration, since other peoples like Iranics have it too; maybe some old Scythian or Sarmatian presence left a bit of an influence. Could be that some of the ancient Daco-Thracian peoples were of this group, or at least part of them, especially the elites. It also depends on the subclades as well though. Was just curious about some of these things.