According to today's New York Times, Russians are coming over the border to take jobs in Latvia that are being left undone thanks to the thousands of Latvians who have moved west since the country joined the EU. (These people are ignoring the "Don't go to Ireland; we need you" ads the Latvian government is running.)
I find this all very interesting. Latvians are uneasy because there is a large Russian minority (nearly 30% of the population) in the country left behind when the USSR collapsed and the Latvian government has been doing all it can to force these Russians to "become" Latvians. The last thing the government and many Latvians want are more Russians in the country.
Yet, the economy is doing well and employers need workers. So, you have illegal immigrants coming from Russia & Belarus. The numbers don't seem to be too large now, but that could change.
What happens if the Latvian economy really takes off over the next few years? Sure, Latvians may stop coming to Ireland, but a quick look at the demographics of Latvia indicates that they will need immigrants even if their young people stop 'going to Ireland'. It seems inevitable that most of those immigrants will be Russian-speakers, but this could cause a lot of strain in Latvia.